Isotherms Mini Unit 

by 2002

Updated January 2008


What is an isotherm?  

What do they look like?  

Interactive Tutorial for drawing Isotherms:

Courtesy of David Babb, Dept. of Meteorology, The Pennsylvania State University. 
This content is part of the Certificate of Achievement in Weather Forecasting and M.Ed. in Earth Sciences programs
offered by the Penn State World Campus. (link:


            (Directions are written by Liz LaRosa,, 2008)

1.  Go to this website and then click on the first link in the first paragraph, or just click here.

2.  A new window will open.

3.  Where it says: "Select isotherm"  Click on the box and choose 50.  Then click "Draw Line".  Watch as the pencil draws a line with temperatures less than 50 degrees on one side, and temperatures greater than 50 on the other side.

4.  Click on the box and choose 80.  This one is different because it shows a closed isotherm.  Inside the circle it is greater than 80 degrees and outside the circle it is less than 80 degrees.

5.  Using your mouse (shown as a pencil on the screen), draw the isotherms for 40 degrees on the computer screen.

6.  Check your work: "Select isotherm"  click on the box and choose 40 degrees.  Then click "Draw Line".  Compare your line to the line drawn.

7.  On your worksheet, draw in the correct isotherm using a pencil.

8.  You can erase or clear the practice lines at any point by using the "erasing" or "clear practice button".  Continue until all isotherms have been drawn in (60 & 70 degrees)

9.  Click on "colorize", and the isotherms will be drawn and colored in.  Color the isotherms on your worksheet also.

Rules for drawing isotherms:

  1. Draw your isotherm in a neat and smooth line instead of a jagged line. (trace lightly in pencil. then go over when done.)
  2. An isotherm should begin and end at an edge of the map, or, alternatively, loop around and close on itself
  3. An isotherm should never branch or fork
  4. Isotherms should be drawn at equal intervals. 2008