Yosemite National Park is definitely worth a visit
Vast forests, blue lakes, towering sequoias, and majestic waterfalls hint at the beauty of Yosemite National Park—a true natural masterpiece.
Mercer Island (WA) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Mercer Island.
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Climate overview of Mercer Island
Temperatures in Mercer Island, Washington State, United States of America, vary greatly throughout the year. August is the hottest month at 25°C (77°F), while December is the coldest at 8°C (46°F).
The city receives considerable rain/snowfall, with around 1045 mm (41 in) annually. November is the wettest month. It has a distinct dry season from July to August, with warm summers and cold winters. The most sunshine falls in July, with an average of 10.4 hours of daily sunshine.
Mercer Island Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Mercer Island - and find the best time to visit.
Monthly Temperature in Mercer Island
The climate in Mercer Island is known for significant temperature differences throughout the year, making the weather dynamic. Typically, average maximum daytime temperatures range from a comfortable 25°C (77°F) in August to a chilly 8°C (46°F) in the coolest month, December.
Nights vary from 14°C (57°F) in August to around 2°C (36°F) during the colder months.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Mercer Island
Mercer Island has a notably wet climate with abundant precipitation, recording 1045 mm (41 in) of rain/snowfall per year. The climate in Mercer Island shows significant variation throughout the year. Expect heavy rainfall in November, the wettest month, with an average of 168 mm (6.6 in) of precipitation over 21 rainy days.
In contrast, the driest month July offers drier and sunnier days, with around 15 mm (0.6 in) of rainfall over 4 rainy days. For more details, please visit our Mercer Island Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Sunshine Hours in Mercer Island
For those who appreciate different seasons, Mercer Island serves as an ideal destination. Expect longer, more sun-filled days in July with an average of 10.4 hours of sunshine daily, and embrace the darker days in December, offering only 1.8 hours of daily sunlight.
Visit our detailed sunshine hours page for more information.
Monthly hours of sunshine
Data from: Seattle, the United States of America (15 KM, 9 Miles).
Daily hours of sunshine
Data from: Seattle, the United States of America (15 KM, 9 Miles).
Daily percentage of sunshine
Data from: Seattle, the United States of America (15 KM, 9 Miles).
Humidity in Mercer Island by Month
The relative humidity is high throughout the year in Mercer Island.
The city experiences its highest humidity in December, reaching 80%. In July, the humidity drops to its lowest level at 65%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Data from: Seattle, the United States of America (15 KM, 9 Miles).
Wind Speed in Mercer Island
The average wind speed over the year ranges from 4 m/s (8 knots) to 5 m/s (10 knots). It is lower in February, April, May, June, July, August, September, October, November and December and higher in January and March. What does this mean?
The mean monthly wind speed over the year (meters per second)
Data from: Seattle, the United States of America (15 KM, 9 Miles).
Best Time to Visit Mercer Island
For comfortable weather, consider visiting Mercer Island in June, July, August and September. Conditions are usually least favourable in January, February, March, November and December.
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
Jan
wet
Feb
cold
Mar
wet
Apr
good
May
very good
Jun
excellent
Jul
excellent
Aug
excellent
Sep
excellent
Oct
mixed
Nov
wet
Dec
wet
- Best overall: June, July, August and September
- Warmest weather: July and August
- Most sunshine: July
- Fewest rainy days: July and August
- Wettest months: January, October, November and December, when rainfall is highest.
- Seasonal pattern: A distinct dry season from July to August, with warm summers and cold winters
Frequently asked questions about the climate in Mercer Island
What is the best time to visit Mercer Island?
June, July, August and September typically offer the most optimal weather in Mercer Island. In contrast, January, February, March, November and December tend to have less optimal conditions. Mercer Island has a distinct dry season from July to August, with warm summers and cold winters.
What temperatures can I expect in Mercer Island?
Daytime highs range from 8°C (46°F) in December to 25°C (77°F) in August. Nighttime lows range from 2°C (36°F) to 14°C (57°F). Temperatures vary considerably through the year.
How much rain does Mercer Island get?
Annual rainfall is around 1045 mm (41 in). November is the wettest month with 168 mm (6.6 in), while July is the driest with 15 mm (0.6 in).
How sunny is Mercer Island?
Mercer Island receives around 2,171 hours of sunshine per year. July is the sunniest month with 312 hours, while December is the cloudiest with just 54 hours. Overall, Mercer Island enjoys abundant sunshine.
Mercer Island 3-Day Forecast
Mercer Island on the map
Mercer Island is highlighted - select any city to see its climate.
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