Heat waves are periods of abnormally hot weather that can pose health risks. They are characterized by temperatures above the 90th percentile for at least two days. Global warming is increasing the frequency and severity of heat waves. During a heat wave, people are at risk of heat-related illnesses like heat exhaustion and heat stroke. Heat waves can also negatively impact infrastructure, agriculture, wildlife and reduce worker productivity. Preparation and mitigation strategies are needed to address the public health and economic challenges posed by increasing heat waves.

1. e-Learning in Heat waves
Professionals

2. Prevention
In the following you will be presented with information on:
• Description of Heatwaves
• What to be aware of
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
2

3. Description
What are heat waves?
• Heat waves are a series of days or temperatures that create a safety hazard
for anyone exposed to the heat. A heat wave can be an extended period of
days with higher than normal temperatures. A heat wave can also be
shorter in length, but with abnormally high temperatures.
• Any time a person is exposed to heat, they are in danger of suffering from
heat exhaustion and heat stroke. These heat-related illnesses have killed
thousands over the last 100 years.
Heat waves characterized by long duration and high intensity have the
highest impact on mortality. During the 2003 heat wave the highest
impacts were observed in the cities of Paris and London.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
3

4. Description
There is no standard definition for a heat
wave.
In Denmark a national heat wave is defined
as a period of at least 3 consecutive days of
which period the average maximum
temperature across more than fifty percent
of the country exceeds 28 °C (82.4 °F).
In Lithuania it is if the heat (heat wave)
reaches extreme event criteria when the
maximum air temperature for 10
consecutive days is 30 ° C or higher.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
4

5. Definition
Most scientists agree that a heat wave
is defined as a period when
maximum apparent temperature and
minimum temperature are over the
90th percentile of the monthly
distribution for at least two days.
Other scientists define heat waves in
more simplified way. They say heat
waves are extended periods of
unusually hot weather that affect
human and animal health as well as
energy use.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
5

6. Global warming
More and more scientists claim that heat
waves are closely connected with global
warming.
"Global warming is bringing more
frequent and severe heat waves, and the
result will be serious for vulnerable
populations," said Dr. Amanda Staudt,
National Wildlife Federation climate
scientist. "That means air pollution in
urban areas could get worse, bringing
increased risk of heart attacks, strokes and
asthma attacks. Children, the elderly, the
poor and people of colour are especially
vulnerable to these effects."
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
6

7. Global warming
Climate models indicate that an
average summer in 2050 will have
even more days topping 32°C.
Scientists project that if global
warming continues to rise, we will
see the following impacts:
• More extreme heat waves.
• Increased urban air pollution.
• More vulnerable natural habitats.
• Negative impacts to agriculture.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
7

8. Global warming
Heat waves have a greater impact on people who are poor, elderly, children,
have asthma or heart disease or live in big cities.
"Global warming is one of the gravest health emergencies facing humanity.
It's life-threatening and it's affecting us now," said Dr. Peter Wilk, MD,
executive director, Physicians for Social Responsibility." The science confirms
that the frequency and duration of heat waves has increased significantly
over the last 50 years. In the United States, heat waves already kill more
people during a typical year than floods, tornadoes and earthquakes
combined. Given these worsening trends, taking decisive action to stop global
warming becomes a medical necessity.“
• Watch the video on the next slide to find out what Climate Change looks
like
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
8

9. Climate change
In the last decade, hot weather records have
occurred three times more often than cold
weather records. The climate change is one
of the most important reasons for that.
Over the past 100 years, heat waves have
caused more deaths than any other natural
hazard. Heat waves also restrict work
capacity and decrease the productivity of
exposed workers. Extreme heat can damage
infrastructure such as electricity distribution
and transport systems, causing follow-on
effects.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
10

10. Climate change
Hot, dry conditions have a major
influence on wildfires – these
conditions are driving up the
likelihood of very high fire danger.
Heat waves can cause drought,
which in turn can also increase
wildfire risk.
Additionally heat waves result in
high energy consumption, as people
use more electricity to power air
conditioners in their home, work and
cars.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
11

11. Climate change
As greenhouse gases continue to
accumulate in the atmosphere,
primarily from the burning of fossil
fuels, more heat is trapped in the lower
atmosphere.
If the current trend in greenhouse gas
emissions continues through the rest of
this century, today’s record-breaking
hot weather will become
commonplace, occurring almost every
summer.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
12

12. Characteristics
Heat waves are a particularly risk for people living in cities because
metropolitan areas can be significantly warmer than neighbouring
countryside areas. Dense urban areas, such as inner city environments, may
typically be 1 to 3°C hotter than surrounding areas.
This phenomenon is known as the “Urban Heat Island” and occurs because of
a decreased amount of plants and increased areas of dark surfaces in urban
environments (sidewalks, roads, etc.). In addition to this is the effect of the
heat produced from vehicles and generators.
The Urban Heat Island effect is generally more prominent during the night
than the day due to e.g. asphalt from the roads that gradually releases heat at
night, so it has a great impact on the likelihood of extreme high minimum
temperatures.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
13

13. Characteristics
We can divide the main reasons of why heat
waves occur into two parts:
1. Air pressure
Most of the world's weather systems are powered
by areas of high and low air pressure. Heat waves
begin with a mass of high atmospheric pressure.
The air from the upper atmosphere is pulled
toward the ground, creating this system of high
pressure. This compresses the air near the
surface, which also increases its temperature.
Because there is no upward flow of air, clouds do
not form, which limits rain and shade. Areas of
high pressure also tend to be less windy, which
keeps the air mass stagnant. This is why heat
waves can last for long periods of time.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
14

14. Characteristics
2. Depletion of Ozone layer
The Ozone layer covers the Earth and
protects it from direct and very harmful sun
rays. Depletion of this layer can bring harm
not only for people (various cancer illnesses
can accur) but also for nature (the land may
become drier, the temperature of the air is
rising, etc.)
We should all be very careful about the
environment in order not to make the Ozone
layer thinner. However everyone can get into
a situation where the heat outside your home
may be above the normal temperature. In
this case you should all know how to behave
and what to do.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
15

15. Characteristics
We can distinguish several features of heat waves:
Unseasonable warmth
Heat waves are generally characterized by
periods of unseasonable warmth. This is
defined as being at least 9 degrees Celsius
higher than the average temperature of a
region, during the same time of year.
Although this type of anomaly is common
and can also happen during the cooler
months, it is generally considered a heat
wave during the warm months when the air
becomes uncomfortably warm.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
16

16. Characteristics
Humidity
• As much as the heat is a factor in a heat wave, so is the humidity.
Humidity measures how much moisture is in the air. Warm air
holds more moisture than cold air and, at higher temperatures,
humidity can be extremely uncomfortable. The reason for this is
that the human body cools itself by the evaporation of sweat.
When the humidity is too high, sweat does not effectively
evaporate, and people can easily overheat.
• The effect of humidity is measured by the heat index, which
describes what the apparent temperature is in high humidity. For
example, at 65 percent humidity, a 35-degree day can feel like it's
45-48 degrees outside
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
17

17. Characteristics
• Heat waves, particularly those
with excessive humidity, can
accompany and possibly worsen
the effects of drought. Heat waves
occur when a ridge of high
pressure sits over a region for an
extended period of time, bringing
down dry, hot air to the ground.
As the air sinks, it warms and
compresses and is very hot by the
time it reaches the surface. This
hot air quickly heats up the
ground, which raises the air
temperature well in excess of the
average daily maximum.
• Since the centre of high pressure
areas are usually cloud-free, the
direct sunlight further raises
daytime temperatures. If humidity
is high, temperatures do not cool
much at night. Nighttime heat
greatly contributes to heat stress
because the body has no relief
from the oppressive conditions.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
18

18. Characteristics
Duration
• In addition to unseasonably warm
temperatures and high humidity,
a heat wave is characterized by its
duration. One unusually warm
day does not make a heat wave.
However, when that heat stays
around for two or more days, it is
considered a heat wave.
• The longer a mass of high
atmospheric pressure sits on an
area, the warmer it can get. In this
respect, heat waves that last many
days or even several weeks can be
particularly dangerous.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
19

19. Effects on environment
Effects on nature
• Like human beings, animals suffer too, particularly when they are left
in the direct sun and they do not get adequate water. Domestic animals
and poultry are especially vulnerable to heat wave.
Temperature, wind speed, humidity, and
solar radiation can all contribute to heat
stress in livestock. In periods of
extreme heat, poultry may lose up to 5%
of their body mass per hour and
rapidly reach their limit of dehydration tolerance.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
20

20. Effects on environment
Effects on nature
• Marine organisms are also affected by the impacts of severe heat. Heat waves can
occur in the surface waters of the ocean, sometimes leading to dramatic impacts
on marine ecosystems. When coral reefs are subject to sea surface temperatures
more than 1-2°C above average summer maximum temperatures, the corals can
bleach and die.
Bleaching events on the Great Barrier Reef have occurred repeatedly since the late
1970’s, where none were observed before the 1970’s. Bleaching events have
contributed to the decline in coral cover observed from 1985 to 2002.
However, corals are not the only marine systems to be affected by heatwaves.
Mortality and reduced reproduction have also been observed in some marine
species. Extreme heat affects each ecosystem differently, however, it may take a
long time to recover after the heatwave or the ecosystem may never return to its
original state.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
21

21. Effects on environment
Effects on nature
• Extreme heat has a negative impact
on grain crops (maize, wheat, and
soya), as well as fruit trees (apple,
cherry, pear) and other plants.
Many plants and fruit trees can have
difficulties because the heat wave
may affect the quality of the fruit.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
22

22. Effects on environment
Effects on agriculture
• Despite the complexity of global food
supply, there are well-established
linkages between growing season
temperatures, precipitation and crop
performance. For wheat, corn and
barley, there is a clear negative
response of global yields to increased
temperatures.
Heat waves can have significant
impacts on agricultural crops and
livestock. High temperatures over
several days can substantially reduce
the crop yield through both direct and
indirect effects.
The direct effect is through:
• damage to the crop’s reproductive
parts, responsible for producing grain,
• reduction in productive potential.
Indirectly, extreme temperatures
increase:
• plant water stress
• photosynthesis, which affects yield and
grain quality, stops functioning and
plants could die.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
23

23. Effects on environment
Impacts on infrastructure
• Extreme heat can have significant impacts on
infrastructure and essential services, especially
electricity transmission and transport systems. Heat
waves increase the energy demand, in particular from
use of air conditioners. Electricity transmission is
affected in such a way:
Transmission lines may become so hot that they
expand and can hang dangerously low.
If this occurs, the electricity flow is decreased to allow
the transmission line to cool and contract.
Ceramic insulators on power lines that are affected by
smoke, moisture, or ash from heat wave associated
wildfires, become less effective and the electricity
supply may be stopped.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
24

24. Effects on environment
Effects on wildfires
• Fire is a natural and beneficial part
of many forest ecosystems, but the
number and intensity of fires today
is challenging fire managers and
forest communities throughout the
world.
Longer fire seasons will result as
spring ends earlier, summer heat
builds up more quickly and warm
conditions extend further into
autumn.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
25

25. Effects on environment
• Drier conditions will increase the
probability of fire occurrence. Fire was
once a healthy, natural part of our
ecosystem, however climate change and
other pressures are causing more
intensified firestorms, causing more
damage and putting wildlife more at risk.
The impacts on wildlife are:
• They can't escape.
• Their habitat is destroyed.
• They undergo major stresses trying to
recover.
• Bigger fires are changing the ecosystem
balance.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
26

26. Impact on humans
Workplace safety and productivity
• The effect of extreme heat is the slowing
down of daily activities and reducing
work productivity, which is an
economically significant factor.
Extreme heat can pose serious health risks
for outdoor workers and for those
working in enclosed indoor spaces
without adequate ventilation. Under
extreme conditions heat stress or even
death can occur.
You can divide the physical effort of jobs
into three categories affected by heat
waves.
Categories:
1. Easy physical work – that could be a job
that is closely connected with sitting or
less physical activity.
2. Physical job of mid-difficulty – the
work connected with bigger physical
activity than usual (more walking,
more moving) and/or moving things
that weigh less than 10 kg.
3. Hard physical job – the job which is
connected with permanent and fixed
physical activity (walking, moving
around, etc.) and/or moving things that
weigh more than 10 kg from one place
to another.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
27

27. Impact on humans
Those workers most at risk during a
heat wave include:
• construction workers
• agricultural workers
• emergency and essential service
workers
• those working outside in the
mining industry
• Watch the video on the next slide to
find out how your body responds to
Heatwaves
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
28

28. Impact on humans
As mentioned before, during physical exertion
in periods of extreme heat, the body can have
difficulty removing the heat generated. This
can lead to the core body temperature rising to
dangerous levels, which furthermore can lead
to heat stress or death.
Extreme heat can also lead to mental health
problems in workers, such as:
• Aggression and confusion
• Psychological distress and other behavioural
changes
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
30

29. Impact on humans
The impacts of extreme heat on workers wellbeing and productivity can also
be measured in economic terms, due to the general slowing down or the
complete stopping of work.
Reduced productivity from future heat waves will not only be costly, but will
force changes in the workplace. Measures such as air conditioning to
workplaces to enhance worker productivity may be costly and unreliable.
Workers may need to take more frequent breaks or work at a slower pace.
As a result, to maintain current productivity levels, it may be necessary to:
• engage greater numbers of workers.
• increase working hours for existing workers.
• change working hours to night shifts to avoid the heat of the day.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
31

30. Impact on humans
Public health
The impact of hot weather and heat
waves on population health depends
upon the level of exposure
(frequency, severity and duration),
the size of the exposed population
and the population sensitivity.
It is therefore not surprising that the
relationship between daily weather
and health varies between
populations and between studies.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
32

31. Impact on humans
Every year thousands of people
suffer from heat stress. Depletion
of salt and electrolyte in the body
may cause heat cramps and hard
work under the direct sun may
lead to heat exhaustion.
Because men sweat more than
women, they are more susceptible
to heat illness because they
become more quickly dehydrated.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
33
People living in urban areas may
be at greater risk from the effects
of a pro-longed heat wave than
people living in rural regions.
While people in rural areas
generally get some relief from the
heat when temperatures fall at
night, urban areas stay warmer.
This is as previously mentioned the
Urban Heat Island effect.

32. Impact on humans
Mortality rises in hot weather, especially
in elderly people.
Around 2.000 additional deaths were
reported in England and Wales during
the major heat wave that affected most
of western Europe in 2003.
Deaths in Paris increased by 140 %. The
sustained period of extreme high
temperatures (including the minimum
temperature) was unique in the
recorded history of Paris and together
with housing designed for cooler
summers, it caused a major public
health crisis.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
34
The recent experience of the heat waves
in Europe demonstrated that even in
high income countries such events can
cause large numbers of deaths in the
absence of a coordinated response to
ensure that elderly people are kept cool
and well hydrated.

33. Impact on humans
Watch the video on the next slide to find out ; Why do deaths in
buildings happen at night during Heatwaves?
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
35

34. Impact on humans
Heat waves or long periods of extreme heat can
have serious impacts on people's health. During
extremely hot weather, it is easy to become
dehydrated (lose too much water from your
body), or for your body to overheat. If this
happens, you are at risk of developing heat
cramps, heat exhaustion or even heat stroke.
It is very important that a person’s body
temperature stays in the range of 36.1 –
37.8°C. If the body temperature rises above
this, a person may develop a heat-related
illness.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
37

35. Impact on humans
• Watch the video on the next slide to see what happens when you get
Heat Stroke
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
38

36. Impact on humans
The body can lose heat by:
• conduction (direct contact of a cooler object
with the skin).
• radiation (via infrared rays).
• convection (through water or air circulating
across the skin).
• evaporation of sweat .
When the temperature of the skin is higher
than the air temperature, the body can lose
heat by radiation, conduction and convection.
However, when the air is hotter than the skin,
the only means by which the body can lose
heat is through sweating (evaporation).
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
40

37. Impact on humans
When the weather is very hot, the body has to work very hard and produce a
lot of sweat to keep itself cool. Under some conditions, sweating just isn’t
enough and a person’s body temperature rises rapidly. This is more likely to
happen when it is humid, or when a person is dehydrated and cannot
produce enough sweat.
In addition, some people cannot cope as well with hot conditions as others.
For example, elderly people and people taking certain medications are less
able to produce sweat. Also young children produce more body heat, sweat
less and have faster rising body temperatures.
Exposure to high temperatures can make existing illnesses seriously worse
(for example trigger a heart attack), cause serious permanent injuries
(damage to the brain or other vital organs) as a result of untreated heat stroke
and, in extreme cases, result in death.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
41

38. Impact on humans
Everyone needs to take care in hot weather, but some people are at higher risk of
heat illness.
The following are listed characteristics of people at higher risk of
serious health effects.
Individual characteristics:
• Over the age of 75
• Infants and young children
• Overweight or obese
• Pregnant or breastfeeding
• Low cardiovascular fitness
• Poor mobility
• Cognitive impairment
• On certain regular medications
• Living by themselves or homeless
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
42

39. Impact on humans
Social characteristics:
• Living alone or socially isolated
• Low socioeconomic status
• Homeless
Occupation and recreational activities:
• Working in a hot environment (e.g. labourers, gardeners, fire
fighters)
• Exercising vigorously in the heat
Chronic diseases:
• Heart disease
• High blood pressure
• Diabetes
• Cancer or kidney disease
• Alcohol and other substance use
• Mental illness
Conditions that affect sweating:
• Heart disease
• Dehydration (e.g. conditions causing diarrhoea)
• Extremes of age
• Skin disorders (sunburn, prickly heat, extensive scarring)
• Cystic fibrosis
• Quadriplegia
• Scleroderma
• Congenital impairment of sweating
• People taking medications with anti-cholinergic effects
Acute illness:
• Dehydration (e.g. gastroenteritis, diarrhoea from other causes)
• Infection, especially with a fever
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
43

40. This educational resource has been produced by the partners of the e-PPR Project (e-Learning for the Prevention, Preparedness and
Response to Natural Disasters) with the support of the Erasmus+ programme.
Unless otherwise stated, this educational resource is licensed under a Creative Commons Attribution-ShareAlike 4.0 International
License. It is attributed to the partners of the e-PPR project. Further information can be found at www.e-ppr.eu
The authors are committed to respecting the intellectual property rights of others, and have taken all reasonable efforts to ensure that
the reproduction of content (text, pictures, etc.) has been done with the full consent of copyright holders and that all copyright holders
are acknowledged in such reproductions. If you feel that your copyright has not been fully respected, please contact us by email at
projectmanager@e-ppr.eu.
If you are going to use parts of the content with materials whose copyright holder(s) is/are not the authors, it is your responsibility to
make sure you do so, respecting the original holder’s copyrights.
This content is the sole responsibility of the project partners and can in no way be taken to reflect the views of the European Union.
e-Learning for the Prevention, Preparedness and Response to
Natural Disasters
44
Copyright Statement