Weather in Seattle in August

Prime time. If you get to pick your dates, August is the one. Highs average 23.9 °C, lows 13.7 °C, and rain falls on 5 days — nothing in the month is working against you.

August ranks 2 of 12 in Seattle. Only July scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain falls on only 5 days, so an itinerary with no wet-weather fallback is a reasonable risk. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

The averages here are honest — no hidden extremes worth planning around. Across the twenty years measured, the hottest August day reached 33.4 °C and the coldest night fell to 8.2 °C, and the wettest single day dropped 27 mm — roughly 93% of the month's rain in one day.

This is the volatile part. August rainfall has ranged from 2 mm to 108 mm across the twenty years measured — a 106 mm spread around an average of 29 mm. The average is real but almost no individual August looks like it, so treat the figure as the middle of a wide range rather than a forecast.

Wind is light at 1.9 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 76%, high enough to notice on the warm days without dominating them.

How August sits in the year

Temperatures hold steady either side: 23.5 °C in July, 23.9 here, 21 in September. Nothing about the timing within the month matters much. Rain is the thing that moves: September brings 5 days more of it, so the earlier half of a flexible trip is the safer half.

Daylight in August

14.3 hours of daylight, losing 1.5 hours across the month. That is between Seattle's extremes of 16 and 8.5 hours, so days are long enough not to constrain the plan.

An inland climate

Despite being inland, the year stays fairly even: 21.9 °C between the year's warmest afternoons and coldest nights.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

August in Seattle versus nearby

If Seattle is one option among several, the nearby comparison is worth making. Maple Ridge is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Vancouver is close enough to be a coin toss — within a degree on temperature, 4 days more rain.

So: August is effectively as good as it gets here — 3 points behind July, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Seattle

See all twelve months in Seattle, or where else to go in August.