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The Climate of Siskiyou County
Siskiyou County has the typical hot, dry summers and cool, wet winters characteristic of Mediterranean climates. However, since the latitude of Siskiyou County (41° N to 42° N) is at the northern extreme of the Mediterranean climate zone and is in a mountainous region, we tend to have colder winters than the average Mediterranean region. Hence, Siskiyou County mainly falls within the Mediterranean highland climate region with much of our winter precipitation falling as snow. The Klamath Mountains occupy the western portion of Siskiyou County. Shasta Valley divides the Klamaths from the Cascade Range. The Modoc Plateau lies east of the Cascades. Elevational differences, along with the distance from our major source of precipitation, the Pacific Ocean, accounts for most of the variability in Siskiyou County's climate. It is readily apparent, when viewing the average yearly precipitation map of Siskiyou County (shown above), that the western portion of Siskiyou County receives the most moisture and it becomes progressively drier eastward. The high elevation and close proximity to the Pacific Ocean results in the Klamath Mountains receiving an average of 40"-60"/year in the valley regions and from 80"-100"/year in the higher elevations. The Shasta Valley lies in a rainshadow of the Klamaths, and thus receives less than 20"/year. As the winter storms move eastward with the westerlies they reach the Cascade Range and the elevational uplift results in relatively high precipitation (about 30"-60"/year) in the Cascades. The Modoc Plateau lies in the rainshadow of the Cascades. By the time the storms have passed over the Coast Ranges (to the west of Siskiyou County), the many ranges of the Klamaths, and the Cascades, most of the moisture has been precipitated out. The Modoc Plateau receives little precipitation, around 10"-20"/year. Also, due to the distance from the moderating influence of the Pacific Ocean, the Modoc Plateau has cold winter temperatures. This part of Siskiyou County is classified as a steppe climate region rather than Mediterranean. Information compiled by Linda Freeman, COS Geography Instructor CLIMATOLOGICAL DATA FOR SISKIYOU COUNTY | CITY | ELEV.
FEET | MEAN TEMP/JAN. | MEAN TEMP/JULY | EXTREME/ MAX | EXTREME/ MIN | ANNUAL PRECIP.. | ANNUAL SNOW | | Montague ShastaValley | 2,640 | 33.8 | 72.5 | 110 | -15 | 12.12 | 8.9 | | Fort Jones Scott Valley | 2,747 | 32.9 | 69.7 | 110 | -23 | 21.78 | 30.4 | | Mt. Hebron Butte Valley | 4,250 | 27.6 | 62.8 | 100 | -22 | 10.89 | 27.6 | | Tulelake Tule Basin | 4,036 | 29.6 | 65.3 | 100 | -27 | 10.21 | 23.5 | Information Provided by Linda Freeman |
Siskiyou Climate 
