Choose the city or region that will be the subject of the climatogram. You can use data from the Weather Channel or the National Weather Weather Service websites for your project.

Draw the three axes of the graph, which will be used to plot the data. For the horizontal axis of the graph, mark off 12 evenly spaced points. These points will represent the 12 months of the year. Mark off two vertical axes on each side of the graph. The right-side axis should mark off the temperature, in degrees Celsius or Fahrenheit. The left-hand axis of the graph should measure the total precipitation.

Mark the average high temperature for each month, and connect these dots with a single, curved line. Repeat this process for the average low temperature of each month. You should be left with two curved lines that roughly parallel each other. Color code each line accordingly -- red for high temperatures and blue for low temperatures. These lines, when drawn, should leave the bottom half of the graph open for your precipitation bars.

Create bars to represent the rainfall data, for each month. Ideally, you may need to adjust the scales of the graph accordingly, to ensure that the bar graph fits neatly underneath the curved lines that represent temperature. Try to minimize empty space as much as possible. When you are finished, all of the graph's data should be clearly presented and without any confusing overlap.

Label all of the axes, such as "Temperature (Degrees C)," Precipitation (cm)" and "Months." Remember to clearly mark the units of measurements for each axis: Fahrenheit or Celsius, inches or centimeters. Write in the names of the months below the bars. Always include a legend, designating which color line corresponds to which set of data.

Give the final graph an appropriate title. This title should clearly indicate what sort of information users can expect to find in the graph and the name of the city or region. You would also do well to list all the sources of the data, for future reference, in either a byline or an appendix.