Seattle weather in August
In August, Seattle has daytime highs averaging 25 °C, nights around 14 °C, with 5.0 wet days. Figures are 1991–2020 climate normals.
- 24.9°C Average high
- 14.0°C Average low
- 5.0days Wet days
- 34mm Rainfall
- 14h Daylight
Daily temperatures through August
How August develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 August | 25.4 °C | 14.3 °C | 13 % |
| 11–20 August | 25.6 °C | 14.3 °C | 13 % |
| 21–31 August | 24.0 °C | 13.5 °C | 21 % |
- Average highs fall from 25.4 °C early in August to 24.0 °C by the end of it.
- Rain is most likely over days 21–31 of August (21 % of days) and least likely over days 1–10 (13 %).
What to expect
| Measure | Typical August | Share of the month |
|---|---|---|
| Days above 25 °C | 15 of 31 | 49 % |
| Days above 30 °C | 1.9 of 31 | 6 % |
| Days below 0 °C | 0 of 31 | 0 % |
| Days with more than 1 mm rain | 5.0 of 31 | 16 % |
Conditions in August
| Measure | Average |
|---|---|
| Mean temperature | 19 °C |
| Record high (1991–2020) | 36 °C |
| Record low (1991–2020) | 8.0 °C |
| Relative humidity | 69 % |
| Wind speed | 12 km/h |
| Cloud cover | 45 % |
Where Seattle ranks in August
| Ranking | Position | Value |
|---|---|---|
| Places with the best weather in North America in August | 3rdof 50 | 94/100 |
| Places with the best weather in the world in August | 47thof 50 | 94/100 |
August compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| June | 20.6 °C | 59 mm | 62 % |
| July | 24.6 °C | 25 mm | 45 % |
| August | 24.9 °C | 34 mm | 45 % |
| September | 21.3 °C | 64 mm | 51 % |
| October | 15.2 °C | 129 mm | 66 % |
See all twelve months for Seattle
- August is the warmest month in Seattle.
- It is the 2nd driest month of the year.
- It ranks 2nd for least cloud cover.
- Days last about 14 hours from sunrise to sunset.
- It rains on 5.0 of 31 days — 16 % of the month.
- Nights are about 11 °C cooler than the middle of the day.
- The hottest August day on record since 1991 reached 36 °C, 11 °C above the usual daytime high.
Nearby destinations in August
QuestionsAugust in Seattle, answered
How warm is Seattle in August?
Daily highs average 25 °C and nights fall to about 14 °C, a spread of 11 °C between afternoon and dawn. That makes August the 1st warmest month of the year here.
Does it rain much in Seattle in August?
August averages 34 mm of rain, spread over about 5 of the 31 days — 16 % of the month. Cloud cover averages 45 % of the sky.
How long are the days in August?
Seattle averages 14 hours between sunrise and sunset in August. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
Data sources and method
- ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
- Open-Meteo — Open-Meteo.com. CC BY 4.0
- NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
- GeoNames — GeoNames.org. CC BY 4.0
- Normal period
- 1991–2020
- Dataset version
- era5-1991-2020-scores1.1
- Last processed
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. Full formulas are on the methodology page.
Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.