Lake Roosevelt is a working reservoir and serves as the main storage reservoir on the Columbia River for the United States. The reservoir is lowered in the spring to make room for the spring runoff, which prevents flooding on the lower Columbia River. The water that enters Lake Roosevelt during the spring is stored in the lake and is used later in the year for power generation and to enhance river flows downstream, protecting endangered species of fish when flows on the Columbia River drop later in the summer and fall.
Operating elevations range from 1208 to 1290 feet in depth. The most up-to-date elevations can be found here. For more information, visit the NOAA Water Level page.
Be prepared for the best of all worlds! A dry, sunny climate is prevalent in the summer months – daylight temperatures typically range from 75 degrees Fahrenheit to 113 degrees Fahrenheit. Beautiful evenings are the norm, with temps ranging from 50 to 80 degrees Fahrenheit. As you travel north on the lake it becomes cooler, with a wetter climate. Spring and fall bring about cooler temperatures, but pleasant nonetheless.
While Lake Roosevelt Adventures is uniquely located in the perfect spots on the lake, we encourage our guests to be prepared as weather can change, sometimes rather dramatically, from one end of the lake to another. (From NPS.gov)
The most accurate weather can be found by searching Wilbur, WA.