Climate and monthly weather forecastSeattle, WA
Climate and monthly weather forecast
The climate of Seattle
Seattle, Washington, is designated under the Köppen climate classification as Csb, which signifies a Mediterranean climate with warm summers. The city's location has a notable influence on the variation in weather parameters throughout the year. Average high temperatures over the year range from 43.7°F (6.5°C) in December to 76.3°F (24.6°C) in August. Meanwhile, average low temperatures fluctuate from 35.1°F (1.7°C) in December to 54°F (12.2°C) in August.The percentage of relative humidity in Seattle also differs considerably over the year, starting from 69% in July and reaching a peak of 85% in January. Furthermore, rainfall observes a contrasting pattern, with the minimal amount occurring in July and August 0.12" (3mm), while the maximum precipitation of 0.87" (22mm) happens in December. Remarkably, despite being in a region known for its rainfall, the city observes just under nine days of rainfall on average per month, with the highest frequency in November at 9.1 days and the lowest in August at 2.8 days.
In terms of sunshine, Seattle receives 10.7 hours per day on average during August, in contrast to December when daylight hours reduce to a mere 8.5 hours per day. On the other hand, wind speeds in Seattle vary marginally, clocking a high of 5.3mph (8.5km/h) in March and a low of 3.5mph (5.6km/h) between July and August.
The best time to visit Seattle
Seattle's climatological data suggests that the months from May to September offer the most conducive conditions for tourists. During this period, the city experiences moderate temperatures ranging from 56.5°F (13.6°C) to 76.3°F (24.6°C). The humidity levels are also lower, between 73% and 75%. Moreover, these months record the least amount of rainfall, with August recording a minimal 0.12" (3mm), while the rainfall days are also at their lowest throughout the year. Also, Seattle experiences the highest levels of sunshine, between 9.2 hours and 10.7 hours daily, which is ideal for outdoor activities and sightseeing.The worst time to visit Seattle
The months between November and February are generally less desirable for tourists due to the prevailing weather conditions. During these months, temperatures drop to average lows between 35.1°F (1.7°C) to 36°F (2.2°C) and highs do not exceed an average of 50.5°F (10.3°C). These months also witness greater precipitation, with average rainfall quantities between 0.59" (15mm) and 0.87" (22mm), and the frequency of rainy days also increases. Moreover, daylight hours are at their lowest, adversely affecting tourism activities.Spring weather in Seattle
Spring in Seattle, between March and May, witnesses a gradual increase in temperatures from an average high of 50.5°F (10.3°C) in March to 64.8°F (18.2°C) in May. This period also sees a decrease in average humidity from 82% to 75%. Rainfall continues to diminish, recording 0.35" (9mm) in March down to 0.39" (10mm) in May. Days gradually become longer with daylight hours ranging from 11.9 hours in March to 15.2 hours in May, allowing more opportunities for outdoor activities.Summer weather in Seattle
Summer, from June to August, is the warmest period in Seattle with average high temperatures rising from 69.1°F (20.6°C) to 76.3°F (24.6°C). Relative humidity is at its lowest during these months, between 69% and 73%. Rainfall reaches its yearly minimum in July and August, reporting a mere 0.12" (3mm), making summer the driest season in Seattle. Despite the overall dry conditions, the city is in full bloom and this is considered an ideal time for tourists.Autumn weather in Seattle
Autumn, from September to November, experiences a decrease in temperatures with an average high curving from 69.6°F (20.9°C) in September to 49.1°F (9.5°C) in November. There is a marked upward shift in humidity from 75% to 84%. Rainfall levels start increasing in this period, with November documenting 0.63" (16mm). Despite the increased rainfall, this season paints a vibrant hue across the city making it attractive for visitors.Winter weather in Seattle
Winter in Seattle, spanning December to February, is the coldest period with average high temperatures within 43.7°F (6.5°C) and 46.2°F (7.9°C), and average lows hovering between 35.1°F (1.7°C) and 36°F (2.2°C). The relative humidity remains fairly high during these months at 84% to 85%. These months also see an escalation in precipitation, with December attaining the maximum average rainfall of 0.87" (22mm). Despite having reduced daylight, this season has its own charm, offering a unique winter experience for visitors.Weather in January
Winter still holds Seattle in its firm grip as the year takes off, though the climate is milder than some other states. This month, temperatures fluctuate between 36°F (2.2°C) and 45°F (7.2°C), making it relatively mild for a winter month. Weather in January »Weather in February
February sees a subtle shift in weather, with temperatures incrementally rising compared to January. It brings a slight increase in sunshine hours and a decrease in both rainfall and snowfall. The weather remains comfortably cool, as it has not yet transitioned fully to spring conditions. Weather in February »Weather in March
March heralds the beginning of spring in Seattle, bringing an aura of freshness and rejuvenation. The shift from winter to spring is subtle - more noticeable in the blooming flora than in the slow rise of temperatures. Still, conditions are a step warmer than February, showing a slight increase in average daily sunshine. Weather in March »Weather in April
April’s warmer temperatures and lower humidity make it a pleasant time for outdoor activities in Seattle. Temperatures typically begin to show a consistent rise, signaling a move away from the winter chill. The reduction in cloud cover accompanying the change in seasons often creates breathtaking sunrise and sunset views from the city’s many vantage points. Weather in April »Weather in May
May, often dubbed "Seattle's secret summer," offers increasingly pleasant weather. There is an increase in daytime temperatures, and the humidity decreases, making conditions ideal for exploring the city’s attractive landscapes and vistas. Weather in May »Weather in June
June ushers in summer in Seattle, with temperatures climbing to the year's warm levels. Sea temperatures begin to rise, tempting beachgoers to the city's inviting shores for some fun in the sun. It is an eventful time, with locals outdoors enjoying the extended daylight and appreciable amount of sunshine. Weather in June »Weather in July
July stands out as the hottest month in Seattle, with temperatures reaching an average high of 75.9°F (24.4°C). Clear skies, along with extended daylight, mean that sunshine is abundant. Low rainfall characterizes this month, making it an ideal period for outdoor activities. Weather in July »Weather in August
August maintains the summer heat, with temperatures nearly mirroring July's highs. Rain becomes even more scarce, and the city revels in clear, sun-drenched days. As the warmest sea temperatures take hold, August asserts itself as an excellent time for swim enthusiasts to take a dip in the calm waters. Weather in August »Weather in September
September in Seattle marks the transition from summer to fall, with a gradual drop in temperature. Days begin to shorten and temperatures start to cool off after the summer’s heat, but the city continues to enjoy fairly sunny and dry conditions. Weather in September »Weather in October
October is characterized by cooler temperatures as Seattle enters the heart of the fall season. Rain returns in slightly greater quantity, but warm and sunny days are still quite typical. This month brings a spectacular display of fall foliage, as leaves turn into vibrant shades of red, orange, and gold. Weather in October »Weather in November
November escorts in the cooler late-autumn weather in Seattle, with a noticeable decrease in temperatures. It marks the transition from fall to winter, with cooler temperatures and a substantial increase in rainfall. Prevailing winds are moderately light, but gusts can occasionally reach up to 8.6mph (13.8km/h). Weather in November »Weather in December
December introduces the winter season in Seattle, bringing colder temperatures and increased cloud cover. With the average lows dipping to 35.1°F (1.7°C), it is the coolest month on the calendar. This period experiences the shortest daylight hours due to the winter solstice, adding to the wintry ambiance. Weather in December »Updated: Jul 31, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
January is the most humid month, with an average relative humidity of 85%.
In Seattle, Washington, during the entire year, the rain falls for 84.2 days and collects up to 5.2" (132mm) of precipitation.
January through March and November are months with snowfall.
In Seattle, during the entire year, snow falls for 4.8 days and aggregates up to 0.94" (24mm) of snow.
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 2.
February is the month with the most snowfall. Snow falls for 1.9 days and accumulates 0.71" (18mm) of snow.
February is the month with the coldest seawater, with an average ocean temperature of 45.3°F (7.4°C).
On Sunday, March 10. 2024, at 2:00 am, Daylight Saving Time starts, 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 Seattle, snow does not fall in April through October and December.
The month with the longest days is June, with an average of 15h and 54min of daylight.
The least humid month is July, with an average relative humidity of 69%.
July and August are months with the least rain when the rain falls for 4.2 days and typically aggregates up to 0.12" (3mm) of rain.
July is the month with the highest UV index, with an average maximum UV index of 6.
Temperature readings reach their annual highs in August, averaging 76.3°F (24.6°C) and a minimum average of 54°F (12.2°C).
The month with the warmest seawater is August, with an average ocean temperature of 53.6°F (12°C).
The month with the most sunshine is August, with an average of 10.7h of sunshine.
December, having an average high-temperature of 43.7°F (6.5°C) and an average low-temperature of 35.1°F (1.7°C), is the coldest month.
The month with the most rainfall is December, when the rain falls for 8.9 days and typically aggregates up to 0.87" (22mm) of precipitation.
December has the shortest days of the year, with an average of 8h and 30min of daylight.
The month with the least sunshine is December, with an average of 4.3h of sunshine.
Average temperature
Seattle, WA
The warmest month (with the highest average high temperature) is August (76.3°F).
The month with the lowest average high temperature is December (43.7°F).
The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (35.1°F).
Average pressure
Seattle, 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:
30.01"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:
30.08"Hg
The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).
Average wind speed
Seattle, WA
- Average wind speed in January:
5.2mph - Average wind speed in February:
5mph - Average wind speed in March:
5.3mph - Average wind speed in April:
4.7mph - Average wind speed in May:
4mph - Average wind speed in June:
3.9mph
- Average wind speed in July:
3.5mph - Average wind speed in August:
3.5mph - Average wind speed in September:
3.9mph - Average wind speed in October:
4.4mph - Average wind speed in November:
5.1mph - Average wind speed in December:
4.8mph
The windiest month (with the highest average wind speed) is March (5.3mph).
The calmest months (with the lowest average wind speed) are July and August (3.5mph).
Average humidity
Seattle, WA
The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).
Average rainfall
Seattle, WA
- Average rainfall in January:
0.71" - Average rainfall in February:
0.59" - Average rainfall in March:
0.35" - Average rainfall in April:
0.39" - Average rainfall in May:
0.39" - Average rainfall in June:
0.24"
- Average rainfall in July:
0.12" - Average rainfall in August:
0.12" - Average rainfall in September:
0.28" - Average rainfall in October:
0.51" - Average rainfall in November:
0.63" - Average rainfall in December:
0.87"
The wettest month (with the highest rainfall) is December (0.87").
The driest months (with the least rainfall) are July and August (0.12").
Average rainfall days
Seattle, WA
- Average rainfall days in January:
8.8 days - Average rainfall days in February:
7.8 days - Average rainfall days in March:
8.9 days - Average rainfall days in April:
8.1 days - Average rainfall days in May:
7 days - Average rainfall days in June:
5.4 days
- Average rainfall days in July:
4.2 days - Average rainfall days in August:
2.8 days - Average rainfall days in September:
6 days - Average rainfall days in October:
7.2 days - Average rainfall days in November:
9.1 days - Average rainfall days in December:
8.9 days
The month with the highest number of rainy days is November (9.1 days).
The month with the least rainy days is August (2.8 days).
Average snowfall
Seattle, WA
The month with the highest snowfall is February (0.71").
The months with the least snowfall are April, May, June, July, August, September, October and December (0").
Average snowfall days
Seattle, WA
- Average snowfall days in January:
1.3 days - Average snowfall days in February:
1.9 days - Average snowfall days in March:
0.5 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:
0.4 days - Average snowfall days in December:
0.6 days
The month with the highest number of snowfall days is February (1.9 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).
Average sea temperature
Seattle, WA
The best month for swimming (with the highest average sea temperature) is August (53.5°F).
The coldest month (with the lowest average sea temperature) is February (45.3°F).
Average daylight / Average sunshine
Seattle, 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 24min - Average sunshine in October:
5h and 36min - Average sunshine in November:
4h and 36min - Average sunshine in December:
4h and 18min
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 18min).
Average sunshine days
Seattle, WA
- Average sunshine days in January:
18.8 days - Average sunshine days in February:
17 days - Average sunshine days in March:
18.6 days - Average sunshine days in April:
18.7 days - Average sunshine days in May:
20.3 days - Average sunshine days in June:
21.8 days
- Average sunshine days in July:
25.8 days - Average sunshine days in August:
25.9 days - Average sunshine days in September:
21.1 days - Average sunshine days in October:
21.1 days - Average sunshine days in November:
16.8 days - Average sunshine days in December:
17.7 days
The month with the most sunshine days is August (25.9 days).
The month with the least sunshine days is November (16.8 days).
Average UV index
Seattle, 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
Seattle, 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
Seattle, WA
The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, November and December (5mi).
