CLIMATE

The Point Reyes Peninsula, similar to the rest of California, is characterized by winter rains and summer drought. The temperature varies little between a winter average of 50º F and a summer average of 55º F. Perhaps the most dramatic feature of the Peninsula's climate, as illustrated by the map above, is its annual rainfall (Figure 4). The interior Olema Valley receives approximately 40 inches of rain per year, while during the same period, the Point Reyes Headlands may receive only 20 inches. What affect, if any, do you think this extreme difference in rainfall might have in the short 20 miles between Olema Valley and the Headlands? (Barbour & Major 1977; Evens 1993; Shuford & Timossi 1989).

Enter one of the Peninsula's surrounding canyons or valleys on an average summer day and you will experience its microclimates first hand. The diurnal temperature between the valleys and the western rangeland can vary by as much as fourteen degrees farenheit (Evens 1993). The Peninsula's unusual biodiversity is greatly effected by these unique microclimates that will be discussed further in the following pages.