Steve Solomon
Chapter 1
Predictably Rainless Summers
In the eastern United States, summertime rainfall can support gardens without irrigation but is just irregular enough to be worrisome. West of the Cascades we go into the summer growing season certain we must water regularly.
My own many-times-revised book Growing Vegetables West of the Cascades correctly emphasized that moisture-stressed vegetables suffer greatly. Because I had not yet noticed how plant spacing affects soil moisture loss, in that book I stated a half-truth as law: Soil moisture loss averages 1-1/2 inches per week during summer.
This figure is generally true for raised-bed gardens west of the Cascades, so I recommended adding 1 1/2 inches of water each week and even more during really hot weather.
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.