Average annual temperature is 11.3 °C
Absolute maximum temperature: 32.5 °C
Absolute minimum temperature: -5.6 °C
Number of sunny days: 163 days
Number of rainy days: 200 days
Number of snow days: 2 days
Look at detailed online map of Mercer Island
* Weather data for Mercer Island United States is based on climate observations for 2026 year
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Absolute maximum temperature (°C) | 13.0 | 13.5 | 15.7 | 22.6 | 28.4 | 28.7 | 29.9 | 32.5 | 26.5 | 24.1 | 15.6 | 14.6 |
| Average daytime temperature (°C) | 8.5 | 7.9 | 10.5 | 12.3 | 20.5 | 22.3 | 26.5 | 26.6 | 21.2 | 16.0 | 10.3 | 9.9 |
| Average temperature (°C) | 5.4 | 4.3 | 5.7 | 7.9 | 14.6 | 15.9 | 19.7 | 20.4 | 15.7 | 11.7 | 7.0 | 7.1 |
| Average night temperature (°C) | 3.0 | 1.7 | 2.3 | 4.9 | 10.2 | 11.4 | 14.3 | 15.6 | 12.4 | 8.8 | 4.6 | 4.7 |
| Absolute minimum temperature (°C) | -4.9 | -5.6 | -2.4 | 1.1 | 6.8 | 8.3 | 11.6 | 13.1 | 8.5 | 0.7 | -1.7 | -0.6 |
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight maximum duration (h) | 9.0 | 10.0 | 12.0 | 14.0 | 15.0 | 15.0 | 15.0 | 14.0 | 13.0 | 11.0 | 9.0 | 8.0 |
| Daylight mean duration (h) | 8.9 | 10.3 | 11.9 | 13.6 | 15.1 | 15.9 | 15.5 | 14.2 | 12.6 | 10.9 | 9.3 | 8.5 |
| Daylight minimum duration (h) | 8.0 | 9.0 | 11.0 | 12.0 | 14.0 | 15.0 | 15.0 | 13.0 | 11.0 | 10.0 | 8.0 | 8.0 |
| Sunshine mean duration (h) | 3.5 | 4.6 | 7.1 | 6.7 | 10.5 | 11.1 | 13.0 | 11.1 | 7.9 | 6.2 | 5.3 | 2.9 |
| Precipitation (mm) | 115 | 75 | 91 | 152 | 27 | 42 | 9 | 38 | 93 | 89 | 158 | 234 |
| Sunny days | 4 | 10 | 7 | 7 | 19 | 20 | 26 | 18 | 14 | 16 | 15 | 7 |
| Rainy days | 26 | 17 | 24 | 23 | 12 | 10 | 5 | 13 | 16 | 15 | 15 | 24 |
| Snow days | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
The best time to visit Mercer Island during the most sunny months:
Months with the longest average daylight duration in Mercer Island:
The largest precipitation sum in Mercer Island is at