This document describes several common weather instruments and what each measures. An anemometer measures wind speed, a barometer measures air pressure, a hygrometer measures humidity, a rain gauge measures precipitation, a thermometer measures temperature, and a wind vane measures wind direction. These tools are important for collecting weather data and understanding current and changing conditions.

1. Weather Instruments
TOOLS USED TO MEASURE AND COLLECT
WEATHER DATA.

2. Anemometer
Measures wind speed like a
speedometer in a car.
The wind catches the little
bowls on the top and spins
them around.
Wind speed is a sign of
changing weather;
especially when a warm or
cold front is moving into an
area.

3. Barometer
A barometer (bah-rom-it-er) measures
air pressure – or the force pushing air
down against the Earth’s surface.
High air pressure causes the needle to
point towards the right side of the
circle to the areas marked “FAIR”,
“DRY” or “VERY DRY”. Days with high
pressure will have few clouds and blue
skies. Precipitation is not likely.
Low air pressure causes the needle to
point to the left side of the circle
towards “RAIN”, “VERY WET” or
“STORMY”. Days with low pressure
will often be overcast or very cloudy
and precipitation is likely.

4. Hygrometer
A hygrometer (high-grom-it-
er) is used to measure the
humidity in the air. Humidity
is caused by water vapor
trapped in the air; especially
on high-pressure days in a
warm air mass.
“Normal” in the photo shows
the most common humidity
levels, as well as the most
comfortable air humidity
levels. Below “normal” and
the air is too dry. Above
“normal” and you feel sticky
and sweaty. The air feels
thick.

5. Rain Gauge
A rain gauge is used to measure the
precipitation over a period of time, and
measurements can be taken in inches or
centimeters.
They are important to know if an area is
getting enough or too much rainfall. Not
enough rainfall over a long period of time can
lead to drought (dr-owt), and too much over a
short period of time can lead to flooding.
Drought is dangerous because it can damage
crops and livestock and reduce drinking water
supply. Floods are dangerous because they can
cause quick and unexpected changes to the
land, they can damage property and harm
people and animals.

6. Thermometer
Thermometers like these
are used to measure air
temperature indoors and
outdoors.
When the red line is very
tall, it means it is warm
or hot.
When the red line is
short, it means it is cool
or cold.
Warm Air Mass Cool Air Mass Cold Air Mass

7. Wind Vane
A wind vane (also known as a
weather vane) is used to tell wind
direction.
When a wind vane points to “N”, as
it appears to do in this picture, it
shows the direction where the wind
is coming from. In this case the
wind is blowing from the north.
The arrow and dog spin around to
change with the wind direction.
A wind vane does not measure
wind speed, but it can show strong
winds by spinning randomly.