Secondary - Heatwaves - Prevention

HEAT WAVES
PREVENTION
SECONDARY LEVEL
e-Learning for the Prevention, Preparedness and Response to Natural Disasters

IN THIS LESSON YOU WILL LEARN
● What are heat waves?
● What causes heat waves?
● Signs of heat waves.
● The impact of heat waves. What to be aware of?
● The most important heatwaves in the world throughout
history

WHAT IS A HEAT WAVE?
.

Do you know what are heatwaves?
The weather is
warming up in the
summertime, the days
are becoming longer
and there's more time
to be outside doing all
kinds of fun things!
But if you're going to
be out in the sun,
especially on a hot day,
you need to stay safe

Do you know what are heatwaves?
Weather is not always the
same. You can tell so by
looking outside or find out
about the weather by
watching weather forecasts
on the TV, Internet, Mobile
phone apps, Radio and so on.
The weather is
warming up in the
summertime, the days
are becoming longer
and there's more time
to be outside doing all
kinds of fun things!
But if you're going to
be out in the sun,
especially on a hot day,
you need to stay safe

Do you know what a heatwave is?
HEAT is energy that
is transferred from one
body to another because of
a difference in
temperature.

Do you know what heatwaves are?
HEAT WAVES are extended
periods of unusually hot weather that
affect human and animal health. A heat
wave can be an extended period of days
with higher than normal temperatures.

Do you know what heatwaves are?
HEAT WAVES are extended
periods of unusually hot weather that
affect human and animal health. A heat
wave can be an extended period of days
with higher than normal temperatures.
However, a heat wave can also be
shorter in length, but with abnormally high
temperatures which bring negative effects
on human health, as well as on nature.

What causes a heat wave?

What causes a heatwave?
CLIMATE CHANGE is one of the
most important factors which cause heat
waves and increase their intensity and
frequency. Heat waves are becoming
hotter, lasting longer and occurring
more often. In the last decade, record hot
weather has occurred three times more
often than cold weather records.

CLIMATE CHANGE is one of the
most important factors which cause heat
waves and increase their intensity and
frequency. Heat waves are becoming
hotter, lasting longer and occurring
more often. In the last decade, record hot
weather has occurred three times more
often than cold weather records. Climate
change is also making heat waves worse
in terms of their impacts on people,
property, communities and the
environment

AIR PRESSURE
DEPLETION OF OZONE LAYER
THERE ARE TWO MAIN REASONS WHY HEAT WAVES
OCCUR

The main reason why heat waves occur is closely
connected with the Jet stream. The jet stream occurs in the
atmosphere at approximately 11 km height between areas
of high and low air pressure. The air on the edges of the
Jet stream is likely to be warmer. Since the high
atmospheric pressure is not marked by lots of clouds, the
surface of the earth can easily get warmer than usual. In
this case, because the layer of cloud above the earth is
very thin or does not exist at all, the possibility to cool the
earth disappears completely and here the conditions for a
heat wave are created.
AIR PRESSURE

The Ozone layer covers the Earth from direct and very
harmful sun rays. Depletion of this layer can bring harm
not only for people (various types of cancer can occur), but
also for the environment (the land may become drier; the
temperature of the air is rising, etc.). So, we should all be
very careful about the environment in order not to make
the Ozone layer thinner.
Depletion of the Ozone Layer

Signs of heat waves

Signs of heat waves
We should all be very careful about
the environment in order not to
make the Ozone layer thinner.
Everyone should know how to behave
and what to do if a heat wave occurs.

Signs of heat waves
We can distinguish several
features of heat waves:

Signs of heat waves
Unseasonable Warmth

Signs of heat waves
Unseasonable Warmth
Humidity

Signs of heat waves
Unseasonable Warmth
Humidity
Duration

Signs of heat waves
UNSEASONABLE WARMTH
Heat waves are generally characterized by periods of
unseasonable warmth. This is defined in different ways
in different countries. Although this can also happen
and be common during the cooler months, it is
generally considered a heat wave during the warm
months when the air becomes uncomfortably warm.
For example, the air temperature in your town or city
reaches 28-30◦ C for couple of days. The weather
forecast on TV or radio does not promise any changes
– according to forecaster such temperature will
remain during the next 4-5 days. So such a period can
be called a heat wave

Signs of heat waves
UNSEASONABLE WARMTH
Heat waves are generally characterized by
periods of unseasonable warmth.

Signs 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.

Signs of heat waves
UNSEASONABLE WARMTH

Signs of heat waves
HUMIDITY
Humidity measures how much moisture is in the air

Signs of heat waves
HUMIDITY
Warm air holds more moisture
than cold air, and at higher
temperatures, humidity can be
extremely uncomfortable.

Signs of heat waves
HUMIDITY
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

Signs of heat waves
HUMIDITY
Heat waves can lead to DROUGHT.
Image courtesy of dan at FreeDigitalPhotos.net

Signs of heat waves
HUMIDITY
Drought and heat, in fact, are inter-related.
According to scientists, in regions where
moisture of the air and soil is reduced, naturally,
the air temperature rises, and this can result in
longer and more intense heatwaves and
droughts.
Image courtesy of dan at FreeDigitalPhotos.net

Signs of heat waves
HUMIDITY
Drought and heat, in fact, are inter-related.
According to scientists, in regions where
moisture of the air and soil is reduced, naturally,
the air temperature rises, and this can result in
longer and more intense heatwaves and
droughts.
If there is enough water in the soil, cooling
connected with the evaporation can slow the
severity of an outcoming heatwave, preventing
the occurrence of extreme heatwaves. Image courtesy of dan at FreeDigitalPhotos.net

Signs of heat waves
HUMIDITY
Heatwaves 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.

Signs of heat waves
HUMIDITY
This hot air quickly heats up the ground, which
raises the air temperature. Since the centre of high
pressure areas are usually cloud-free, the direct
sunlight raises daytime temperatures further.

Signs of heat waves
HUMIDITY
This hot air quickly heats up the ground, which
raises the air temperature. Since the centre of high
pressure areas are usually cloud-free, the direct
sunlight raises daytime temperatures further.
If humidity is high, temperatures do not cool
much at night. Night-time heat greatly contributes
to overall humidity.

Signs of heat waves
DURATION
In addition to unseasonably warm temperatures and
high humidity, a heat wave is characterized by its
duration.

Signs of heat waves
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 way, heat waves last many days or even
several weeks and can be particularly dangerous.
In addition to unseasonably warm temperatures and
high humidity, a heat wave is characterized by its
duration.

Signs of heat waves - DURATION

Signs of heat waves
Which picture do you think shows hot summer weather and which shows a heat wave?

THE IMPACT OF HEAT WAVES.
What to be aware of?.

The impact of heat waves
Each summer, different areas of the world
experience unseasonably warm temperatures for
extended periods of time. Many news stories
follow these heat waves, pointing out several
public health dangers. Heat waves have been
known to cause medical problems and even
deaths. Additionally, heat waves result in higher
energy consumption, as people use more electricity
to power air conditioners in their homes, work
places and cars.

What to be aware of:
Heat waves are a particularly important 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 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 the heat produced from
vehicles and generators. The Urban Heat Island effect
is generally more prominent during the night than the
day, so its major impact is to increase the likelihood of
extreme high minimum temperatures.

Heat waves can be dangerous for adults over 65,
children under 4, and people who suffer from
heart disease. 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.

Going into more details, we have to
mention that elderly people are
particularly at risk during a heatwave.
This is because ageing decreases
tolerance to heat:

tolerance to heat:
•thirst is sensed late,

tolerance to heat:
•the sweating reaction is delayed,

tolerance to heat:
•the sweating reaction is delayed,
•and the number of sweating glands
is reduced.

Heat waves can have direct and
indirect impacts on people’s
health.

The direct impact of heat waves on human health
The main health effects of a heat wave
result from the body not being able to
effectively cool itself. Without proper
cooling, a person can suffer from heat
exhaustion and eventually heat stroke.
Without enough fluid intake, a person can
suffer dehydration. This often occurs
when the body sweats out more water
than it takes in. The elderly, particularly
those who have problems with their heart,
can be especially vulnerable during a heat
wave.

The higher body temperature occurs when natural
body's cooling process is affected by the heatwave,
when the body cannot evaporate itself properly by
sweating, especially if humidity is high.
The main health effects of a heat wave result from the body not
being able to effectively cool itself.

If core body temperature rises to 38
degerees for several hours, heat
exhaustion occurs and mental and
physical capacity becomes impaired.

If core body temperature rises to 42,
even for just a few hours, heat stroke and
death can result.

Heat waves lasting even a few days,
especially if coupled with high night-
time temperatures (for example, above
20°C or lower 30°C), can cause serious
health impacts.

health impacts.
The warm nights are particularly
important because our bodies do not get
the chance to recover.

health impacts.
The warm nights are particularly
important because our bodies do not get
the chance to recover.
It is the cumulative effects over a few
days of an intense heat wave that lead
to serious health impacts and deaths –
and people tend to see these after the
worst of the heat wave has passed.

In summary, we can note that:
• People can suffer from heat cramps, heat exhaustion or even
heat stroke

heat stroke
• When a heat wave occurs the body can lose lots of water –
dehydration may occur

heat stroke.
• When a heat wave occurs the body can lose lots of water –
dehydration may occur.
• Also, when trying to cool yourself during the intensive heat by
drinking lost of cold water you can catch the flu

* Some information which help
you to recognise heat cramps:
- They are muscular pains
and spasms that usually occur in
the legs. Such spasms can occur
even while having rest or at
night time.
- Panic can occur because
people do not know how to
behave in such a situation.
Heat cramps
Heat cramps are often an early sign
that the body is having trouble with
the heat.

Signs which will help to
recognise that a person is
suffering from the heat
exhaustion:
- cool, moist, pale, flushed
skin;
- headache;
- nausea;
- dizziness;
- weakness and exhaustion.
Heat exhaustion
Heat exhaustion is a more severe condition
than heat cramps.

Heat exhaustion
Heat exhaustion is a more severe condition
than heat cramps.
Heat exhaustion often
affects athletes,
firefighters, and
factory workers,
those wearing heavy
clothing in a hot,
humid environment.

Signs which will help to recognise that a person
is suffering from the heat stroke are:
- extremely high body temperature;
- red skin which may be dry or moist;
- changes in consciousness;
- rapid, weak pulse and rapid, shallow
breathing;
-vomiting
Heat stroke
Heat stroke is a life-threatening condition that usually
occurs by ignoring the signals of heat exhaustion.
Heat stroke develops when the body’s systems are
overwhelmed by heat and begin to stop functioning.

Heat stroke and Heat exhaustion
Heat exhaustion and heat
stroke are very similar. That is
why it is sometimes difficult
to identify and separate what
exactly happened to a person.
The main differences between
heat exhaustion and heat
stroke are:

* Signs which will help to
recognise that a person is
suffering from dehydration
are:
- increased thirst;
- increased sweating;
- dry mouth and
swollen tongue;
- weakness;
- confusion;
- fainting;
- head aches.
Dehydration Dehydration is the loss of large amounts of
liquid from the body.
* It occurs when the amount of water
leaving the body is greater than the amount
being taken in.

The indirect impact of heat waves on human health
There are a number of indirect effects that extreme
heat has on our health:

• It can be various infectious diseases transmitted by
insects.

insects.
• It is very important to mention that extreme heat
can lead to power outages, which in turn can lead to
a loss of air-conditioning, refrigeration and cooling,
affecting homes and food outlets.

insects.
• It is very important to mention that extreme heat
can lead to power outages, which in turn can lead to
a loss of air-conditioning, refrigeration and cooling,
affecting homes and food outlets.
• Harmful bacteria in food grow more quickly in
warm temperatures, increasing the possibility of
gastrointestinal illnesses from food that is kept in
such warm conditions without refrigeration.

The impact of heat waves on infrastructure
Extreme heat can have significant impacts on
infrastructure and essential service, especially
electricity transmission and transport systems.
Heat waves test ability of the infrastructure to
withstand the pressures of increased energy
demand (in particular from use of air
conditioners).
Electricity transmission can also be affected as
transmission lines may become so hot that they
expand and can hang dangerously low and have
to be switched off.

The impact of heat waves on the environment
Heat waves can cause significant damage to nature and the
environment:

environment:
Some species of animals can disappear.

environment:
New species of insects and animals that are heat-resistant
appear.

environment:
appear.
Other animals change their usual lifestyle and behaviour.

environment:
appear.
Other animals change their usual lifestyle and behaviour.
Fires in open places (forests, meadows) become more
frequent

The impact of heat waves on nature
Like human beings, animals can also suffer, 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, birds may lose up to 5% of
their body mass per hour and rapidly reach their limit of
dehydration tolerance.

Marine organisms are also affected by the impacts of severe heat.
Heatwaves 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 1970s where none were observed before
1970. 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 their original state

Extreme heat has a negative impact on
grain crops (maize, wheat, and soya) as
well as fruit trees (apple, cherry, pear) and
may affect the quality of the fruit. Other
plants also feel the negative impact of heat
waves.

It is now well known that many bumblebee species are
threatened in Europe and in North America.
Various theories have been presented to explain this
regression. Some scientists say that many bumblebee
species are disappearingis due to synthetic fertilisation.
However, since 2002, it has been observed that a great
number of situations where local droughts and heat
waves occurred in France, UK, Scandinavia, Turkey,
have lead to very strong local reductions of the
bumblebee fauna.
As they are the most exposed to heat waves, they can be
the most sensitive to this risk

The impact of heat waves on wildfires
If weather gets really hot and dry it can increase
the possibility of wildfires
Wildfire has very negative impact on wildlife
•Animals cannot excape

•Habitats of local animals will be destroyed

•Different plants and plantlife are either destroyed
completely or need a great amount of time to
recover

recover
•Fires get hotter, bigger and more frequent

recover
•Big fires are changing the ecosystem balance

recover
•Big fires are changing the ecosystem balance
•Entire forests are being destroyed and it takes
hundreds of years for mature forests to return

The most important heatwaves in the
world throughout history

The most important heatwaves in the world
throughout history
Marble Bar heatwave, 1923-1924.
The world record for the longest sequence of days
above 100◦ Fahrenheit (or 37.8◦ on the Celsius
scale) is held by Marble Bar in the inland Pilbara
district of Western Australia.
The temperature, measured under standard
exposure conditions, reached or exceeded the
century mark every day from 31st October 1923 to
7th April 1924, a total of 160 days.

The „Dust Bowl“years of 1930-1936.
Some of the hottest summers on record in the
United States. Nationally, around 5000 deaths
were associated with the heatwave. What lead to
the “Dust Bowl”?
1) The lack of rain that parched the earth and
killed vegetation;
2) Poor land management.
throughout history

throughout history
The famous summer of ’76 in the UK.
It was a period of nine weeks; the weather was
consistently dry, sunny and hot. It should also be
remembered that summer of the 1976 marked the
culmination of a prolonged drought which had
begun in April, 1975

throughout history
Europe, 2003.
More than 20 000 people died after a record-
breaking heatwave left Europe sweltering in
August 2003. The period of extreme heat is
thought to be the warmest for up to 500 years, and
many European countries experienced their
highest temperatures on record.

throughout history
Lithuania, 2006.
Extreme heat affected wildlife in Kuršių Nerija,
the Curonian Spit National Park. At that time 236
hectares of the territory of the National park
burned away in just in five days. Even today the
area is only partially replanted. Further wildfires
occurred after the 2006 fire and the soil was
damaged and is not as heat-resistant now as it
was before.

throughout history
Drought and wildfires in Russia in 2010.
After record warm temperatures, drought,
wildfires, and poor air quality during July 2010,
the dismal conditions continued through mid-
August across western Russia. At the beginning of
August, 676 square miles (1 740 square km) were
burning with over 600 active fires.

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