Mercer Island, WA Weather & Climate Normals
Mercer Island's real weather, in one number
Mercer Island, WA scores 56/100 on this site's reading of NOAA's own 30-year normals: strongly seasonal. Comfortable weather is limited to a shorter window; summers, winters, or precipitation swing wide. 5 of the year's 12 months average between 55 and 75°F, the range this site counts as mild.
Mercer Island's hottest and coldest months
Mercer Island's hottest month is Aug, averaging 68°F; its coldest is Dec, averaging 42°F, a 25.8°F swing across the year, a middling gap by national standards.
Mercer Island's weather across the year
| Month | Avg high | Avg low | Precip |
|---|---|---|---|
| Jan | 49°F | 37°F | 5.21in |
| Feb | 51°F | 37°F | 3.71in |
| Mar | 55°F | 39°F | 3.94in |
| Apr | 60°F | 44°F | 2.89in |
| May | 67°F | 49°F | 1.98in |
| Jun | 71°F | 54°F | 1.22in |
| Jul | 77°F | 58°F | 0.56in |
| Aug | 77°F | 58°F | 0.83in |
| Sep | 72°F | 54°F | 1.37in |
| Oct | 61°F | 46°F | 3.49in |
| Nov | 53°F | 40°F | 5.8in |
| Dec | 48°F | 36°F | 5.49in |
May, Jun, Jul, Aug, and Sep are the best time to see Mercer Island at its mildest; the rest of the year, plan around Dec's cold.
Rain and snow in Mercer Island
Over a typical year, Mercer Island sees about 36.49in of precipitation a year across roughly 154 days with measurable rain or snow. That station has no snowfall reading, so none is shown rather than assumed.
Where Mercer Island ranks
Mercer Island ranks 758 of 4876 US cities in this dataset for comfort score, and 45 of 125 within WA. About 25,302 people live there.
If you need tomorrow's forecast, not the 30-year average
Everything above is a 30-year average from Seattle Boeing Fld, WA US, 4.0 miles from Mercer Island, not a prediction for any specific day.
More on how this is worked out
Why some cities show no snow or rain figure · How the comfort score is calculated