SC.5.E.5.3 Weather Observations

SC.5.E.7.3: Recognize how air temperature, barometric pressure, humidity, wind speed and direction, and precipitation determine the weather in a particular place and time.

How do we describe weather?

Weather is a description of what is happening in the atmosphere at a certain place and time. The weather at your school at lunch time might be different than it was at breakfast. It might also be different from the school across town.

The way that weather is described is based on air temperature, barometric pressure, humidity, wind speed and direction, and precipitation. Each of those factors can be measured and recorded. When weather observers gather data, there are certain tools they use to gather each of those measurements.

Air temperature is how warm or cool the air is. This can be measured with a thermometer. Temperature is recorded as both degrees (°) Fahrenheit (°F) and degrees Celsius (°C).

Barometric pressure is the weight of the Earth’s atmosphere pushing down. Pressure is important because high pressure prevents clouds from forming and low pressure makes it easier for clouds to form. Because of this effect, high pressure generally means sunny weather, and low pressure generally means stormy weather. The lowest pressures are at the center of storms like hurricanes. Barometric pressure is measured with a tool called a barometer.

Humidity is the amount of water vapor the air can hold. If you live in Florida, you are familiar with the hot, humid days of summer. The air feels sticky and wet. It holds a lot of water vapor. Water vapor is water in the form of a gas. At night, when the Sun goes down the air begins to cool. As the air cools, it can hold less water, and so the humidity level rises sharply. At 100% humidity, the water vapor in the air begins to condense on all surface it touches. This condensation is called dew. Humidity is measured with a tool called a hygrometer and recorded as a percentage: the percentage of water vapor the air can hold.

Wind speed and direction are important to know. If there is a thunderstorm on the horizon, it is good to know if the wind is blowing the storm toward you or away from you. Wind speed is measured using a tool called an anemometer, and recorded as miles per hour, mph. Higher winds speeds are usually part of stormy weather. As with low pressure, the highest wind speeds are usually in strong storms like hurricanes and tornados. Wind direction is measured as the direction the wind is blowing from. If a wind is blowing 25 mph from the north, that is how it is recorded.

There are four forms of precipitation. All four forms of precipitation can fall in Florida, but some of them are rare in southern Florida. Rain is liquid water that falls across the state and can happen any time of year. Rain falls heavily during Florida’s rainy season May through November. During the dry season of December through April, rain falls far less than it did the rest of the year, but it still falls. Snow, sleet, and hail are the three solid forms of precipitation that can fall from clouds. We will look more closely at rain, snow, sleet, and hail in a separate unit.

Together, all these factors describe the weather in a particular time and place. Air temperature, barometric pressure, humidity, wind speed and direction, and precipitation are all factors of weather that can be measured and recorded.