If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content


Review your understanding of weather in this free article aligned to NGSS standards.

Key points:

  • Weather is the state of the atmosphere at a given place and time. Weather is defined by factors such as temperature, rain, and wind.
  • Changes in weather are caused by the movement of air masses. An air mass is a large body of air with uniform temperature and humidity. In general, air masses move from areas of high pressure to areas of low pressure.
  • As air masses move, they collide and form weather fronts.
    • A cold front is formed when a cold air mass moves into a warm air mass. Cold fronts usually bring cool temperatures and heavy rain or thunderstorms.
    • A warm front is formed when a warm air mass moves into a cold air mass. Warm fronts usually bring warm temperatures and moderate rain.
  • Scientists make weather predictions by collecting current weather data and inputting it into computer models. Because weather is so complex, these predictions are only probabilities and not certain outcomes.
An afternoon thunderstorm.
Dramatic thunderstorms often occur at cold fronts. Image credit: Nordseher on Pixabay, Pixabay License.

Want to join the conversation?