Before you decide to do outdoor activities, it is important that you know what kind of weather it will be. If you look out and the sky is sunny without any clouds, you might predict, or be able to tell beforehand, what the weather will be like for the next hour. However, just a look in the sky won’t tell you what is in store for the next few days.

Meteorologists are the people who study weather. They predict what the weather will be like for the next few days. Before they can predict they have to collect information.

We have learned how to measure temperature, air pressure, precipitation, wind speed and direction, and humidity. Meteor- ologists collect this same information from many places, not just one. They know that the weather in other places influences the weather where we are. Many meteorologists get this information from the National Weather Service. This is a government agency that has weather stations collecting information from all over the U.S.

Weather balloons, radar, and satellites are three tools that collect information. Weather balloons collect information from high in the air.

Radar sends radio waves into the air. They bounce off of rain and snow. Radar is used to find where precipitation is and where it is moving.

Satellites high above the earth’s air collect and send information about the weather all over the world.

Meteorologists need information about air masses to predict weather. An air mass is a large amount of air that has the same temperature and humidity. It can be warm or cold. It can have a large amount of water vapor or a small amount. Air masses are so large that two or three different air masses can cover most of the U.S.

Meteorologists also need information about fronts to predict the weather. A front is the line where two air masses meet. The air masses do not mix together but stay separate. A cold air mass often causes thunderstorms. Clouds from a warm air mass often cause a steady rain.

Meteorologists use information about the weather to predict what the weather is going to be like. This prediction is called a forecast. One way they predict weather is to look at the weather in the west. Air masses that cause weather usually move from west to east.

Meteorologists know the kinds of weather that often happen with certain air pressures, air masses, and fronts. High pressure areas often have fair weather. Low pressure areas often have clouds and precipitation.

A warm air mass that comes from over the Gulf of Mexico might bring hot, humid weather on a summer day. A cold air mass from over Canada might bring cooler weather. Thunderstorms and snowstorms often happen at a cold front. Steady rain or snow often happen at a warm front.

Meteorologists study the direction air masses are moving. They study where high pressure areas and low pressure areas are moving. They try to predict what air mass, front, and air pressure are moving into your area. Then they predict what the temperature, chance of precipitation, and wind might be.