 Keswick Reservoir is prone to rapid rises and falls, while alternately receiving releases from Shasta Dam and providing water to Keswick Dam's power generators and to meet downstream water demands.The climate in Shasta County can be characterized as hot and dry in the summer, and cool and wet in winter, with the best climate occurring during the spring and fall seasons, by virtue of average annual rainfall and temperatures.The area receives average annual precipitation of about 69 inches, with the period of heaviest precipitation occurring from October through March, while June through September sees very low rainfall and reduced inflow of water to the dam's reservoir.