Climate and monthly weather forecastMercer Island, WA
Climate and monthly weather forecast
Weather in January
January, like December, is a frosty winter month in Mercer Island, Washington, with an average temperature varying between 35.2°F (1.8°C) and 44.4°F (6.9°C). The beginning of January reveals an average high-temperature of a still frosty 44.4°F (6.9°C), showing minimal deviation from the previous month. Weather in January »Weather in February
The last month of the winter, February, is another chilly month in Mercer Island, Washington, with an average temperature varying between 34.5°F (1.4°C) and 46°F (7.8°C). In February, the average high-temperature registers at a still chilly 46°F (7.8°C), nearly identical to January's 44.4°F (6.9°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 max 50.5°F (10.3°C) and min 36.9°F (2.7°C). At the onset of March, Mercer Island records an average high-temperature of a cool 50.5°F (10.3°C), showing little deviation from the preceding month. Weather in March »Weather in April
April is a refreshing spring month in Mercer Island, Washington, with temperature in the range of an average high of 55.9°F (13.3°C) and an average low of 39.7°F (4.3°C). With the transition into April, Mercer Island experiences a subtle uplift in average high-temperatures, adjusting from a cool 50.5°F (10.3°C) in March to a refreshing 55.9°F (13.3°C). Weather in April »Weather in May
The last month of the spring, May, is a refreshing month in Mercer Island, Washington, with an average temperature ranging between max 64.6°F (18.1°C) and min 44.1°F (6.7°C). The beginning of May signals a minor rise in the average high-temperature, moving from a refreshing 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 an average temperature varying between 47.5°F (8.6°C) and 69.3°F (20.7°C). Mercer Island's average high-temperature in June is a pleasant 69.3°F (20.7°C), indicating a subtle variation from May. Weather in June »Weather in July
July in Mercer Island, Washington, is a warm summer month, with an average temperature fluctuating between 76.1°F (24.5°C) and 51.8°F (11°C). Entering July, Mercer Island notices a subtle temperature elevation, with the average high-temperature advancing from June's pleasant 69.3°F (20.7°C) to a moderately hot 76.1°F (24.5°C). Weather in July »Weather in August
The last month of the summer, August, is also a moderately hot month in Mercer Island, Washington, with an average temperature ranging between max 76.6°F (24.8°C) and min 53.4°F (11.9°C). Mercer Island, Washington, experiences its highest average temperatures in August, reaching a peak of 76.6°F (24.8°C) and a minimum of 53.4°F (11.9°C). Weather in August »Weather in September
The first month of the autumn, September, is still a pleasant month in Mercer Island, Washington, with an average temperature fluctuating between 50°F (10°C) and 70°F (21.1°C). Mercer Island's transition into September involves a gentle shift in temperature, receding from a moderately hot 76.6°F (24.8°C) in August to an agreeable 70°F (21.1°C). Weather in September »Weather in October
October, like September, is another refreshing autumn month in Mercer Island, Washington, with temperature in the range of an average low of 44.2°F (6.8°C) and an average high of 58.6°F (14.8°C). Mercer Island in October demonstrates a small temperature transition, adjusting from an average high of an agreeable 70°F (21.1°C) in September to a refreshing 58.6°F (14.8°C). Weather in October »Weather in November
The last month of the autumn, November, is also a frosty month in Mercer Island, Washington, with temperature in the range of an average high of 48.6°F (9.2°C) and an average low of 39°F (3.9°C). The shift from October to November involves a decrease in the average high-temperature, dropping from a mild 58.6°F (14.8°C) to a frosty 48.6°F (9.2°C). Weather in November »Weather in December
The first month of the winter, December, is also a frosty month in Mercer Island, Washington, with an average temperature ranging between min 34.7°F (1.5°C) and max 42.8°F (6°C). Mercer Island notes the coldest temperatures in December, with a high average of 42.8°F (6°C) and a low of 34.7°F (1.5°C). Weather in December »Updated: Feb 14, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
With an average relative humidity of 85%, January is the most humid month.
Throughout the year, in Mercer Island, Washington, there are 119.1 rainfall days, and 11.97" (304mm) of precipitation is accumulated.
Months with snowfall in Mercer Island are January through March, November and December.
In Mercer Island, during the entire year, snow falls for 7 days and aggregates up to 3.27" (83mm) of snow.
January, February, November and December, with an average maximum UV index of 2, are months with the lowest UV index in Mercer Island.
February is the month with the most snowfall. Snow falls for 3 days and accumulates 1.77" (45mm) of snow.
On Sunday, March 10. 2024, 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 3. 2024, at 2:00 am, and the time zone reverts from PDT to PST.
In Mercer Island, snow does not fall in April through October.
The month with the longest days is June, with an average of 15h and 54min of daylight.
July is the least humid month in Mercer Island, Washington, with an average relative humidity of 69%.
July is the month with the least rainfall in Mercer Island. Rain falls for 5.5 days and accumulates 0.24" (6mm) of precipitation.
With an average maximum UV index of 6, July is the month with the highest UV index.
Mercer Island's August weather, marked by an average high temperature of 76.6°F (24.8°C) and an average low temperature of 53.4°F (11.9°C), is the warmest in the year.
With an average of 10.7h of sunshine, August has the most sunshine of the year.
The month of December, characterized by an average high of 42.8°F (6°C) and a low of 34.7°F (1.5°C), is recognized as the coldest in Mercer Island.
The month with the most rainfall in Mercer Island, Washington, is December, when the rain falls for 12.5 days and typically aggregates up to 2.01" (51mm) of precipitation.
The month with the shortest days in Mercer Island is December, with an average of 8h and 30min of daylight.
December has the least sunshine of the year, with an average of 4.2h of sunshine.
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).
Average pressure
Mercer Island, WA
- Average pressure in January:
30.1"Hg - Average pressure in February:
30.06"Hg - Average pressure in March:
30.01"Hg - Average pressure in April:
30.04"Hg - Average pressure in May:
30.02"Hg - Average pressure in June:
30.02"Hg
- Average pressure in July:
30.03"Hg - Average pressure in August:
30"Hg - Average pressure in September:
30.01"Hg - Average pressure in October:
30.04"Hg - Average pressure in November:
30.04"Hg - Average pressure in December:
30.09"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is August (30"Hg).
Average wind speed
Mercer Island, WA
- Average wind speed in January:
5mph - Average wind speed in February:
4.8mph - Average wind speed in March:
5.1mph - Average wind speed in April:
4.5mph - Average wind speed in May:
3.9mph - Average wind speed in June:
3.7mph
- Average wind speed in July:
3.5mph - Average wind speed in August:
3.4mph - Average wind speed in September:
3.7mph - Average wind speed in October:
4.2mph - Average wind speed in November:
4.9mph - Average wind speed in December:
4.7mph
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).
Average humidity
Mercer Island, WA
The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).
Average rainfall
Mercer Island, WA
- Average rainfall in January:
1.54" - Average rainfall in February:
1.34" - Average rainfall in March:
1.02" - Average rainfall in April:
1.06" - Average rainfall in May:
0.79" - Average rainfall in June:
0.63"
The wettest month (with the highest rainfall) is December (2.01").
The driest month (with the least rainfall) is July (0.24").
Average rainfall days
Mercer Island, WA
- Average rainfall days in January:
11.8 days - Average rainfall days in February:
11.3 days - Average rainfall days in March:
13.7 days - Average rainfall days in April:
12.3 days - Average rainfall days in May:
10.1 days - Average rainfall days in June:
8.9 days
- Average rainfall days in July:
5.5 days - Average rainfall days in August:
4.1 days - Average rainfall days in September:
7.5 days - Average rainfall days in October:
10.5 days - Average rainfall days in November:
10.9 days - Average rainfall days in December:
12.5 days
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).
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").
Average snowfall days
Mercer Island, WA
- Average snowfall days in January:
1.3 days - Average snowfall days in February:
3 days - Average snowfall days in March:
1 days - Average snowfall days in April:
0.1 days - Average snowfall days in May:
0 days - Average snowfall days in June:
0 days
- Average snowfall days in July:
0 days - Average snowfall days in August:
0 days - Average snowfall days in September:
0 days - Average snowfall days in October:
0 days - Average snowfall days in November:
0.5 days - Average snowfall days in December:
1.1 days
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).
Average daylight / Average sunshine
Mercer Island, WA
- Average daylight in January:
9h and 0min - Average daylight in February:
10h and 18min - Average daylight in March:
11h and 54min - Average daylight in April:
13h and 42min - Average daylight in May:
15h and 12min - Average daylight in June:
15h and 54min
- Average daylight in July:
15h and 30min - Average daylight in August:
14h and 12min - Average daylight in September:
12h and 30min - Average daylight in October:
10h and 48min - Average daylight in November:
9h and 18min - Average daylight in December:
8h and 30min
The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).
- Average sunshine in January:
4h and 24min - Average sunshine in February:
4h and 30min - Average sunshine in March:
6h and 18min - Average sunshine in April:
8h and 6min - Average sunshine in May:
9h and 12min - Average sunshine in June:
9h and 24min
- Average sunshine in July:
10h and 36min - Average sunshine in August:
10h and 42min - Average sunshine in September:
9h and 18min - Average sunshine in October:
5h and 30min - Average sunshine in November:
4h and 36min - Average sunshine in December:
4h and 12min
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).
Average sunshine days
Mercer Island, WA
- Average sunshine days in January:
17.1 days - Average sunshine days in February:
13.8 days - Average sunshine days in March:
15.8 days - Average sunshine days in April:
14.8 days - Average sunshine days in May:
18.5 days - Average sunshine days in June:
18.8 days
- Average sunshine days in July:
24.1 days - Average sunshine days in August:
24.9 days - Average sunshine days in September:
20.5 days - Average sunshine days in October:
18.6 days - Average sunshine days in November:
16.6 days - Average sunshine days in December:
17.4 days
The month with the most sunshine days is August (24.9 days).
The month with the least sunshine days is February (13.8 days).
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).
Average cloud cover
Mercer Island, WA
The month with the most cloud cover is December (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 25).
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).
