Isolines - Temperatures in the U.S.

http://www.nc-climate.ncsu.edu/edu/k12/.IsobarIsotherm

 

This map shows isolines that depict lines of equal temperature; more specifically, we refer to these isolines as isotherms.  The different colors represent 10 degrees Fahrenheit, ranging from -30 to 100 degrees F.  We can tell from this map that the U.S. was colder in the North from February 25 to March 3, 2001 (between 0 and 20 degrees F for the most part) than in the Southeast (around 70-80 degrees F).