The graphs below show five year periods of mean monthly temperatures for Napa County, California and Yamhill County, Oregon. The top graphs show temperatures beginning in January 1895 and those below, beginning in January 2000. The maps show 5-year monthly average temperatures across the western United States for the growing months April thru October for the same time periods as the graphs. Use the selection menu to view temperatures for each month. 

1) Begin with April and examine the changes in month-to-month average temperatures for the five year period beginning in 1895 with those beginning in 2000. Briefly describe the changes in general across the western United States and then more specifically in Napa and Yamhill counties.

2) The temperature graphs share several common characteristics. Most obviously, they are periodic - a similar repeating pattern. How frequently does the basic pattern recur in each graph; that is, what is its period? Visualize a horizontal line in each graph representing the middle temperature value. What is that value in each graph? How far above or below the middle value in each graph are the maximum and minimum temperatures? This value is called the amplitude of the curve.

3) Compare the graphs both place-to-place and across time. What general differences do you notice between the two counties and are those differences the same in both time periods? What differences do you notice over time and are those differences the same for both counties?

4) Periodic behavior is common - a Ferris wheel goes round and round, tides fluctuate up and down, the seasons come and go. Identify three other naturally occurring phenomena that show periodic behavior.