Temperature is the measure of heat or cold in a place. It is measured using a thermometer.

Types of Thermometers

• Maximum thermometer – Shows the highest temperature of the day. It contains mercury.
• Minimum thermometer – Shows the lowest temperature of the day. It contains coloured alcohol.

These thermometers are kept in a Stevenson screen – a wooden box painted white to reflect sunlight and give accurate readings.

How to Measure Temperature

For maximum temperature:

1. Place the maximum thermometer outside in a shaded area (not in direct sunlight)
2. Leave it until evening
3. Read where the mercury has risen to the highest point
4. Record the temperature in degrees Celsius (°C)

For minimum temperature:

1. Place the minimum thermometer outside in a cool area, close to the ground
2. Leave it overnight until early morning
3. Read where the alcohol has dropped to the lowest point
4. Record the temperature in degrees Celsius (°C)

Recording Temperature

Keep a simple table like this:

Humidity is the amount of water vapour (moisture) in the air. It is measured in percentage (%) using an instrument called a hygrometer.

Types of Hygrometers

• Digital hygrometer – Shows humidity as a number on a screen
• Dry and wet bulb hygrometer – Uses two thermometers to calculate humidity

How to Measure Humidity Using a Dry and Wet Bulb Hygrometer

1. Wrap the lower part of one thermometer with muslin cloth and dip it in water (wet thermometer)
2. Leave another thermometer unwrapped (dry thermometer)
3. Place both thermometers outside in a clear area
4. Wait 5-10 minutes
5. Read both temperatures
6. Calculate the difference between the two readings
7. Use the difference to determine humidity level

Interpreting Humidity Readings

• No difference between readings = very high humidity (air cannot hold more moisture)
• Small difference (below 40%) = high humidity
• Large difference (above 70%) = low humidity
• Difference between 40-70% = average humidity

Rain is measured using a rain gauge. The instrument collects raindrops and measures the amount in millimetres (mm).

How to Measure Rainfall

1. Place the rain gauge cylinder inside a container dug into the ground
2. Position the funnel on top of the cylinder
3. Leave the gauge 30 centimetres above the ground
4. After rain stops (within 24 hours), check the cylinder
5. If the cylinder is full, pour the water into a measuring cylinder
6. Read the measurement in millimetres
7. Record the amount on a rainfall chart

Recording Rainfall

Wind is air moving from areas of high atmospheric pressure to low atmospheric pressure.

Wind Direction

Wind direction is measured using a wind vane. The arrow points to the direction from which the wind is coming.

How to measure wind direction:

1. Look at the arrow on top of the wind vane
2. Check the cardinal directions (North, East, South, West) marked below
3. The arrow shows where the wind is coming from
4. If the arrow points South, it means the wind is blowing from South to North (South wind)

Wind Speed

Wind speed is measured using an anemometer. It has cups that rotate when wind blows. The faster the cups spin, the stronger the wind.

How to measure wind speed:

1. Hold or place the anemometer in an open area
2. Watch the cups rotate
3. Read the wind speed on the gauge (in km/h or m/s)
4. Record the speed

Atmospheric pressure is the force created by the weight of air pushing down on Earth's surface. It is measured in millibars using a barometer.

Types of Barometers

• Mercury barometer – Uses mercury in a glass tube
• Aneroid barometer – Uses a metal box that expands and contracts
• Digital barometer – Uses electronic sensors

How to Measure Atmospheric Pressure

1. Place the barometer at weather station or outside area
2. Read the pressure on the scale or digital display
3. Record the pressure in millibars

Understanding Pressure Changes

• When temperature increases, atmospheric pressure decreases
• When temperature decreases, atmospheric pressure increases
• Difference in pressure between two areas causes wind to blow

A student in Dodoma recorded the following weather data for three days:

From this data, we can see that:

• Tuesday was the wettest day with 15mm of rain
• Tuesday had the lowest pressure, which explains the rain and high wind speed
• Wednesday had the highest pressure and lowest wind speed

In Tanzania, farmers in regions like Morogoro or Mbeya use weather measurements to plan their farming activities. For example, a coffee farmer checks the humidity and rainfall records to decide when to harvest beans or when to dry them. If the humidity is too high (above 80%), the beans may not dry properly and could develop mold, causing loss. By recording daily temperature and rainfall, a farmer can also predict the best planting season and protect crops from weather-related damage.