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.
Weather Data
Current Conditions
|
Partly Cloudy, 39°F | Humidity: 93% | Dewpoint: 37°F |
| Wind Speed: CALM | Heat Index: 39°F | ||
| Barometer: 30.31 in. | Wind Chill: 39°F |
Weather Forecast
 | Tonight: Partly cloudy this evening then becoming mostly cloudy. Patchy fog. Lows 30 to 40. South wind to 10 mph shifting to the southeast after midnight. | |
| Lo: 36°F | ||
 | Hi: 50°F | Sunday: Partly sunny in the morning then clearing. Patchy morning fog. Highs in the upper 40s to mid 50s. Northeast wind to 10 mph. |
| Lo: 36°F | ||
 | Hi: 50°F | Monday: Sunny. Patchy morning fog. Highs in the upper 40s to mid 50s. Light wind. |
| Lo: 36°F | ||
 | Hi: 51°F | Tuesday: Mostly cloudy with a chance of rain. Highs in the lower 50s. |
| Lo: 36°F | ||
| Hi: 49°F | Wednesday: Mostly sunny. Highs in the upper 40s. |
| Lo: 39°F | ||
| Hi: 49°F | Thanksgiving day: Mostly sunny. Highs in the upper 40s. |
| Lo: 39°F | ||
| Hi: 49°F | Friday: Mostly sunny. Highs in the upper 40s. |
| Lo: 40°F |
Moon, Sunrise and Sunset
 |
Moon Phase: Waning Crescent Moon | Civil Twilight: 6:50 AM PST |
Sunrise: 7:25 AM PST |
| Sunset: 4:24 PM PST |
Civil Twilight: 4:59 PM PST |
Normal Climate
Normal Temperatures
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max °F | 46.9 | 50.5 | 54.5 | 59.3 | 64.9 | 69.5 | 74.5 | 74.9 | 69.9 | 60.3 | 51.5 | 46.5 | 60.3 |
| Mean °F | 41.5 | 43.8 | 46.9 | 50.9 | 56.6 | 61.1 | 65.5 | 66.0 | 61.3 | 53.4 | 46.0 | 41.3 | 52.9 |
| Min °F | 36.0 | 37.1 | 39.2 | 42.5 | 48.2 | 52.7 | 56.4 | 57.1 | 52.6 | 46.4 | 40.4 | 36.1 | 45.4 |
Normal Precipitation
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Inch | 5.24 | 4.09 | 3.92 | 2.75 | 2.03 | 1.55 | 0.93 | 1.16 | 1.61 | 3.24 | 5.67 | 6.06 | 38.25 |
