Climate and monthly weather forecast
Mercer Island, WA

Weather in January

January, like December, is another chilly winter month in Mercer Island, Washington, with temperature in the range of an average low of 35.2°F (1.8°C) and an average high of 44.4°F (6.9°C). In January, the average high-temperature is almost the same as in December - a still chilly 44.4°F (6.9°C). Weather in January »

Weather in February

February, the last month of the winter in Mercer Island, is another chilly month, with an average temperature varying between 34.5°F (1.4°C) and 46°F (7.8°C). In February, the average high-temperature is essentially the same as in January - a still frosty 46°F (7.8°C). Weather in February »

Weather in March

March, the first month of the spring in Mercer Island, is a cool month, with an average temperature ranging between min 36.9°F (2.7°C) and max 50.5°F (10.3°C). In Mercer Island, the average high-temperature in March is almost the same as in February - a fresh 50.5°F (10.3°C). Weather in March »

Weather in April

April in Mercer Island, Washington, is a moderate spring month, with temperature in the range of an average low of 39.7°F (4.3°C) and an average high of 55.9°F (13.3°C). In April, the average high-temperature marginally rises from a fresh 50.5°F (10.3°C) in March to a moderate 55.9°F (13.3°C). Weather in April »

Weather in May

May, the last month of the spring in Mercer Island, is a comfortable month, with an average temperature fluctuating between 44.1°F (6.7°C) and 64.6°F (18.1°C). In Mercer Island, the average high-temperature in May slightly increases from a mild 55.9°F (13.3°C) in April to an enjoyable 64.6°F (18.1°C). Weather in May »

Weather in June

June, the first month of the summer in Mercer Island, is a pleasant month, with temperature in the range of an average high of 69.3°F (20.7°C) and an average low of 47.5°F (8.6°C). In Mercer Island, the average high-temperature in June is almost the same as in May - an agreeable 69.3°F (20.7°C). Weather in June »

Weather in July

July is a moderately hot summer month in Mercer Island, Washington, with an average temperature ranging between min 51.8°F (11°C) and max 76.1°F (24.5°C). In July, the average high-temperature marginally rises from an agreeable 69.3°F (20.7°C) in June to a moderately hot 76.1°F (24.5°C). Weather in July »

Weather in August

August, the last month of the summer in Mercer Island, is also a moderately hot month, with temperature in the range of an average high of 76.6°F (24.8°C) and an average low of 53.4°F (11.9°C). August is the warmest month, with an average high-temperature of 76.6°F (24.8°C) and an average low-temperature of 53.4°F (11.9°C). Weather in August »

Weather in September

September, the first month of the autumn in Mercer Island, is still a pleasant month, with an average temperature varying between 70°F (21.1°C) and 50°F (10°C). In September, the average high-temperature marginally drops from a moderately hot 76.6°F (24.8°C) in August to a pleasant 70°F (21.1°C). Weather in September »

Weather in October

October, like September, is a moderate autumn month in Mercer Island, Washington, with an average temperature fluctuating between 58.6°F (14.8°C) and 44.2°F (6.8°C). In October, the average high-temperature drops from a pleasant 70°F (21.1°C) in September to a moderate 58.6°F (14.8°C). Weather in October »

Weather in November

November, the last month of the autumn in Mercer Island, is also a frosty month, with an average temperature varying between 48.6°F (9.2°C) and 39°F (3.9°C). In November, the average high-temperature drops from a mild 58.6°F (14.8°C) in October to a frosty 48.6°F (9.2°C). Weather in November »

Weather in December

December, the first month of the winter in Mercer Island, is still a chilly month, with an average temperature ranging between max 42.8°F (6°C) and min 34.7°F (1.5°C). The coldest month is December, with an average high-temperature of 42.8°F (6°C) and an average low-temperature of 34.7°F (1.5°C). Weather in December »
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FAQ

What is the most humid month in Mercer Island?

January is the most humid month, with an average relative humidity of 85%.

How many days does it rain in Mercer Island?

Throughout the year, in Mercer Island, Washington, there are 119.1 rainfall days, and 11.97" (304mm) of precipitation is accumulated.

When does it snow in Mercer Island?

January through March, November and December are months with snowfall.

How many days does it snow in Mercer Island?

In Mercer Island, during the entire year, snow falls for 7 days and aggregates up to 3.27" (83mm) of snow.

When is the lowest UV index in Mercer Island?

January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index.

What is the snowiest month in Mercer Island?

The month with the most snowfall in Mercer Island, Washington, is February, when snow falls for 3 days and typically aggregates up to 1.77" (45mm) of snow.

When is Daylight Saving Time (DST) in Mercer Island?

On Sunday, March 12. 2023, at 2:00 am, Daylight Saving Time starts in Mercer Island, and the time zone changes from PST to PDT. Daylight Saving Time ends Sunday, November 5. 2023, at 2:00 am, and the time zone reverts from PDT to PST.

When it does not snow in Mercer Island?

In Mercer Island, Washington, snow does not fall in April through October.

When are the longest days in Mercer Island?

June has the longest days of the year in Mercer Island, with an average of 15h and 55min of daylight.

What is the least humid month in Mercer Island?

July is the least humid month, with an average relative humidity of 69%.

What is the driest month in Mercer Island?

The month with the least rainfall is July, when the rain falls for 5.5 days and typically collects 0.24" (6mm) of precipitation.

When is the highest UV index in Mercer Island?

July is the month with the highest UV index, with an average maximum UV index of 6.

What is the warmest month in Mercer Island?

With an average high-temperature of 76.6°F (24.8°C) and an average low-temperature of 53.4°F (11.9°C), August is the warmest month in Mercer Island, Washington.

What month has the most sunshine in Mercer Island?

The month with the most sunshine in Mercer Island is August, with an average of 10.7h of sunshine.

What is the coldest month in Mercer Island?

The coldest month in Mercer Island, Washington, is December, with an average high-temperature of 42.8°F (6°C) and an average low-temperature of 34.7°F (1.5°C).

What is the rainiest month in Mercer Island?

December is the month with the most rainfall. Rain falls for 12.5 days and accumulates 2.01" (51mm) of precipitation.

What is the month with the shortest days in Mercer Island?

With an average of 8h and 31min of daylight, December has the shortest days of the year.

What is the month with the least sunshine in Mercer Island?

The month with the least sunshine in Mercer Island is December, with an average of 4.2h of sunshine.

Average temperature
Mercer Island, WA

Average temperature - Mercer Island, WA

The warmest month (with the highest average high temperature) is August (76.6°F).
The month with the lowest average high temperature is December (42.8°F).

The month with the highest average low temperature is August (53.4°F).
The coldest month (with the lowest average low temperature) is February (34.5°F).

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Average pressure
Mercer Island, WA

Average pressure - Mercer Island, WA

The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).

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Average wind speed
Mercer Island, WA

Average wind speed - Mercer Island, WA

The windiest month (with the highest average wind speed) is March (5.1mph).
The calmest month (with the lowest average wind speed) is August (3.4mph).

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Average rainfall
Mercer Island, WA

Average rainfall - Mercer Island, WA

The wettest month (with the highest rainfall) is December (2.01").
The driest month (with the least rainfall) is July (0.24").

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Average rainfall days
Mercer Island, WA

Average rainfall days - Mercer Island, WA

The month with the highest number of rainy days is March (13.7 days).
The month with the least rainy days is August (4.1 days).

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Average snowfall
Mercer Island, WA

Average snowfall - Mercer Island, WA

The month with the highest snowfall is February (1.77").
The months with the least snowfall are April, May, June, July, August, September and October (0").

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Average snowfall days
Mercer Island, WA

Average snowfall days - Mercer Island, WA

The month with the highest number of snowfall days is February (3 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average daylight / Average sunshine
Mercer Island, WA

Average daylight / Average sunshine - Mercer Island, WA

The month with the longest days is June (Average daylight: 15h and 55min).
The month with the shortest days is December (Average daylight: 8h and 31min).

The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is December (Average sunshine: 4h and 12min).

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Average sunshine days
Mercer Island, WA

Average sunshine days - Mercer Island, WA

The month with the most sunshine days is August (24.9 days).
The month with the least sunshine days is February (13.8 days).

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Average UV index
Mercer Island, WA

Average UV index - Mercer Island, WA

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average visibility
Mercer Island, WA

Average visibility - Mercer Island, WA

The months with the highest visibility are May, June, July, August and September (6mi).
The months with the lowest visibility are January, February, March, April, October, November and December (5mi).

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