LESSON 2: ISOTHERMS

Will it be warm outside tomorrow?

Certain weather maps allow us to view warm and cold areas in an easy fashion. One helpful weather map contains isotherms. An isotherm is a line connecting locations with equal temperature. Isotherm maps show where temperatures are relatively high and low, and also where temperature changes are gradual or dramatic over a distance.

This image shows an example of a weather map containing 60° and 70° isotherms. The large black lines are called isotherms. They are typically placed at intervals of 10 degrees Fahrenheit.

Exercise 2:

Select Image 2 and print out the map with temperature readings.

1. Determine which 10 degree intervals will be necessary to use for this map.
2. Draw in the isotherms on the map you have printed out. Label each isotherm.

Isotherms can be used to identify air masses (large areas of the lower atmosphere with similar weather). Air masses are generally referred to as cold or warm. Cold air masses are colder in the center, and warm air masses are warmer in the center.

3. Name a state over which a cold air mass is located?
4. Name a state over which a warm air mass is located?

Air masses are also categorized as dry or humid. Humid air masses develop over ocean waters. Dry air masses come from large land areas. An air mass found over the Gulf of Mexico would be humid and warm. An air mass located in central Canada in winter would be dry and cold.

5. How would you describe the air mass moving into the United States from Canada?

Activities (Lessons)

Image Credits:

Maps from The Weather Channel
Maps from Tiger Census Maps

Written by: Gene Rempel and Mike Hanson

Last Modified by NASA: September 19, 1998