Tanoak grows in a climate broadly classified as humid. Annual  precipitation, however, is seasonal and varies from 1020 to 2540  min (40 to 100 in). Some precipitation is snow. Summer and early  fall are dry and the winter rainy. From June through September  rainfall totals less than 25 min (1 in) a month. In fact,  precipitation during these months amounts to only 5 percent of  the year's total. Most of the precipitation-about 70  percent-falls between November and February.
    Average mean daily temperatures range from 2° to 6° C  (36° to 42° F) during January and 16° to 23°  C (60° to 74° F) in July. The season free of killing  frosts begins between March 8 and April 30 and ends between  October 20 and November 20, varying in length between 160 and 249  days. Over a 30-year period the maximum temperature recorded at  183 in (600 ft) elevation in the center of tanoak's area of  maximum development was 45° C (113° F).