Have you ever watched the weather forecast on TV? Have you ever checked the weather app on your phone while getting ready for school so you knew if you should wear a coat or carry an umbrella? Weather describes the current conditions of the atmosphere.

The following picture is from the weather channel app and describes the weather for conditions for a city in Texas on January 18, 2012.

Source: Weather Channel App

What is humidity? What is dew point and how is it calculated? How is the direction and speed of wind determined? In this section, we will explore the answers to these questions.

As you can see from the picture, weather involves more than whether it is going to rain or what the temperature will be. Weather is produced by the interaction of four factors.

Video segment. Assistance may be required. Watch the following video to learn about these 4 factors.

Source: Our World: What is Weather?, NASAeClips, YouTube

Interactive exercise. Assistance may be required. The following sections review each factor affecting weather. Click on each icon to learn more.