Mercer Island, WA Weather
Mercer Island, WA climate is mild during summer when temperatures tend to be in the 60's and cold during winter when temperatures tend to be in the 40's.
The warmest month of the year is August with an average maximum temperature of 74.90 degrees Fahrenheit, while the coldest month of the year is January with an average minimum temperature of 36.00 degrees Fahrenheit.
Temperature variations between night and day tend to be fairly limited during summer with a difference that can reach 18 degrees Fahrenheit, and fairly limited during winter with an average difference of 12 degrees Fahrenheit.
The annual average precipitation at Mercer Island is 38.25 Inches. Winter months tend to be wetter than summer months. The wettest month of the year is December with an average rainfall of 6.06 Inches.