Seattle weather in August
August in Seattle: warm, dry, with clean air — one of the best months to visit.
Updated September 2026 · climate normals from ERA5 reanalysis
#2 of 12 months in Seattle · #22 of 1413 destinations to visit in August · comfort 95/100 (tier S)
- Days
- 25°C
- Nights
- 15°C
- Wet days
- 2
- Sun
- 11.4 h
- Humidity
- 67%
- Daylight
- 14 h

Traveller notes on Seattle in August
Seattle-forum threads on August are almost giddy about the weather - this and the two months around it are the reliably dry, sunny stretch of the year, with posters calling a soggy day genuinely rare and temperatures running warm without the humidity that makes other cities miserable in summer. The one recurring caveat has nothing to do with rainfall: more than one thread flags wildfire smoke as the real risk, a haze that can roll in and ruin an otherwise perfect week with no warning. Cruise-ship crowds pack Pike Place Market and the Space Needle on port days. The record backs the dry read completely: 25.2C days, 14.7C nights, just 12mm total across 1.6 days, 11.4 hours of sun and an AQI of 44 - though that AQI can spike hard on a bad smoke day, which the average doesn't show.
Other months in Seattle
Regulars describe this as the most variable month of the year here, unlike the more settled fall and winter, with two genuinely distinct outcomes possible on any given day - sunny and into the low 70s Fahrenheit, or overcast with highs stuck in the upper 50s to low 60s. Our row backs the mild, changeable average across that range, 19.1C over 9.5C nights, with 34mm of rain across 5.3 days. Regulars are consistent this is still a genuinely good time to visit, flowers in full bloom and springlike energy throughout the city, with layering the standard advice given how unpredictable a specific day can turn out. The record: humidity 74 percent, 10.8 hours of sun, a 12.6 kph wind and AQI 44.
Regulars call this one of the city's best-looking months on paper, and are specific about why: the rains that define this region typically hold off until mid-October, and the first week of the month is often the driest and warmest stretch, with the back half cooling off a little as it goes. Our row backs the shift, 21.4C over 12.3C nights, with 35.5mm of rain across 5.6 days - a real total, but light next to what regulars describe arriving a month later. Evenings call for a light jacket or sweatshirt once the sun goes down. The one caveat some years bring is wildfire smoke drifting in from regional fires, not present every September but enough that regulars mention checking air quality before a trip built around outdoor views. The record: 9.5 hours of sun, a 12.3 kph wind and AQI 40.
Juneuary is the local word for the version of this month that feels like January, and the local claim is that summer does not start until the 5th of July - the same joke the Portland board tells, two hundred kilometres south. The instruction that follows is precise: the 30th of June is a different month from the 1st, so come at the end. Our row is kinder than the nickname. Rain is 29.5mm across 5.1 days, and there are 11.6 hours of sun inside 15.9 of daylight, so the grey is brief showers between sun breaks rather than a ceiling. What June lacks is warmth - 21.6C by day, 12C at night. The record: humidity 71 percent, a 12.5 kph wind and AQI 39.
Seattle forum threads describe February as genuinely mixed - some stretches bring drizzly, overcast, grey days typical of the region's wet season (which runs roughly mid-October through April), while other years bring a welcome week or so of milder, lighter-sun weather that winter-weary locals specifically look forward to. Snow chances were described as relatively low by this point in winter, with January and early February the more likely window for any accumulation. One consistent tip from posters familiar with the wider region: the northern Olympic Peninsula tends to run drier and sunnier than Seattle proper in February, a worthwhile alternative for anyone chasing better odds of sun.
Year-round notes are on Seattle's overview. Add your own note from Seattle's card on the map.
Seattle climate normals — August
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Seattle in August
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
Peak crowdsMount Rainier wildflowers, Seafair, Summer break in United States(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Seattle's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Best weatherSeattle's weather peaks June–August, best around July.
August includes Salmon at the Ballard Locks.
Best weatherFair weatherToughest weather
What's on in Seattle in August
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Nature
Salmon at the Ballard Locks
15 Jun – 20 Sep · usuallyWildlife seasonSockeye run through the fish ladder in early summer, chinook and coho into September, and the viewing windows below the locks are free and busy. Numbers vary wildly year to year. Source ↗
- Season
The dry months
5 Jul – 15 Sep · usuallyDry seasonThe rain effectively stops after the Fourth of July and holds off until well into September. Everything outdoors in this city is scheduled around those ten weeks.
- Nature
Mount Rainier wildflowers
15 Jul – 20 Aug · usuallyWildflowers & bloomsCrowdedParadise and Sunrise flower for about a month once the snowpack finally clears, usually from mid-July. Timed entry applies to the park in summer and the meadows are strictly stay-on-the-path.
- Festival
Seafair
28 Jul – 9 Aug · usuallyMotorsport weekendCrowdedClosuresHydroplane racing on Lake Washington and the Blue Angels overhead on the first weekend of August. The I-90 bridge closes for the air show and the whole east side plans around it. Source ↗
- Hazard
Wildfire smoke
1 Aug – 20 Sep · usuallySmoke seasonLate summer smoke from fires in eastern Washington, Oregon or British Columbia settles into the basin and can hold for days. It is the one thing that spoils the best weather of the year here. Source ↗
Nearby, and something's on
Within 300 km of Seattle — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Seattle?
Seattle in August — FAQ
- Is August a good time to visit Seattle?
- August in Seattle: warm, dry, with clean air — one of the best months to visit. It ranks #2 of 12 months for Seattle on SeasonMap's comfort score (95/100).
- What is the weather like in Seattle in August?
- In August, Seattle averages a daily high of 25.2°C and a low of 14.7°C, with about 11.5 mm of rain over roughly 1.6 rainy days.
- What is the air quality in Seattle in August?
- Seattle has a mean US Air Quality Index of about 44 in August.
Within 300 km: Olympic National Park's Subalpine wildflowers around 20 Jun – 10 Aug, and Victoria, BC's Whale watching season around 1 May – 15 Oct.