Summertime Rainfall West of the Cascades (in inches)*
Location April May June July Aug. Sept. Oct.
Eureka, CA 3.0 2.1 0.7 0.1 0.3 0.7 3.2
Medford, OR 1.0 1.4 0.98 0.3 0.3 0.6 2.1
Eugene, OR 2.3 2.1 1.3 0.3 0.6 1.3 4.0
Portland, OR 2.2 2.1 1.6 0.5 0.8 1.6 3.6
Astoria, OR 4.6 2.7 2.5 1.0 1.5 2.8 6.8
Olympia, WA 3.1 1.9 1.6 0.7 1.2 2.1 5.3
Seattle, WA 2.4 1.7 1.6 0.8 1.0 2.1 4.0
Bellingham, WA 2.3 1.8 1.9 1.0 1.1 2.0 3.7
Vancouver, BC 3.3 2.8 2.5 1.2 1.7 3.6 5.8
Victoria, BC 1.2 1.0 0.9 0.4 0.6 1.5 2.8
*Source: Van der Leeden et al., _The Water Encyclopedia,_ 2nd
ed., (Chelsea, Mich.:Lewis Publishers, 1990).
Defined scientifically, drought is not lack of rain. It is a dry
soil condition in which plant growth slows or stops and plant
survival may be threatened. The earth loses water when wind blows,
when sun shines, when air temperature is high, and when humidity is
low. Of all these factors, air temperature most affects soil
moisture loss.
Daily Maximum Temperature (F)*
July/August Average
Eureka, CA 61
Medford, OR 89
Eugene, OR 82
Astoria, OR 68
Olympia, WA 78
Seattle, WA 75
Bellingham, WA 74
Vancouver, BC 73
Victoria, BC 68
*Source: The Water Encyclopedia.
The kind of vegetation growing on a particular plot and its density
have even more to do with soil moisture loss than temperature or
humidity or wind speed. And, surprising as it might seem, bare soil
may not lose much moisture at all.
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