Seattle, WA weather in September
In September, Seattle sees highs around 71°F and lows around 53°F: mild, with some rain. Expect about 9 wet days. Great for outdoor plans.
- Normal high
- 71°F
- Normal low
- 53°F
- Wet days
- 9
- 1.7 in total
- Muggy days
- 0
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 75°F | 67°F |
| Normal low | 56°F | 50°F |
| Chance of a wet day | 25% | 34% |
| Sunrise / sunset | 6:28 am / 7:50 pm | 7:07 am / 6:51 pm |
| Daylight | 13.4 h | 11.7 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical September day
- 6 am56°Fdew point 51°F
- 9 am61°Fdew point 52°F
- Noon67°Fdew point 52°F
- 3 pm70°Fdew point 50°F
- 6 pm67°Fdew point 50°F
- 9 pm62°Fdew point 51°F
NOAA hourly normals (local standard time) from Seattle Boeing Fld (5 mi away); average wind 5 mph.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F23 of 30
- Beach dayshigh 80-95°F, under 0.05 in of rain, afternoon wind under 15 mph3 of 30
- Hot dayshigh 90°F or more0 of 30
- Muggy daysdaily mean dew point 65°F or more0 of 30
- Wet daysat least 0.01 in of rain or melted snow9 of 30
- Notable rainat least 0.10 in5 of 30
- Freezing nightslow 32°F or below0 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 1.7 in; a dry September brings about 0.8 in and a wet one about 2.0 in (25th and 75th percentiles). About 1 day brings half an inch or more.
How September varies from year to year
- Warmest September, 1991-20202017: average high 75°F
- Coolest September1996: average high 67°F
- Wettest September2013: 5.0 in
- Driest September1991: 0.02 in
- Highest reading91°F (September 10, 2020)
- Lowest reading40°F (September 30, 2019)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 77°F | 71°F | 61°F |
| Normal low | 57°F | 53°F | 47°F |
| Wet days | 6 | 9 | 15 |
| Comfortable days | 22 | 23 | 7 |
| Daylight | 14.2 h | 12.6 h | 10.8 h |
Highs change by -6°F from August and -10°F into October.
Nearby alternatives in September
- Warmer: Leavenworth, WA78 mi · high 78°F · 4 wet days
- Drier: Leavenworth, WA78 mi · high 78°F · 4 wet days
- Cooler: Port Angeles, WA62 mi · high 66°F · 9 wet days
How Seattle ranks in September
- Normal high335th warmest of 378 cities; 5th of 9 in Washington
- Wet days239th driest of 378
- Comfortable days8th most of 342
What to pack for Seattle in September
- A rain jacket or umbrella – rain on about 9 days
Heating and cooling
September has 107 heating degree days and 24 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Seattle in September?
The normal high is 71°F and the normal low is 53°F. From 1991 to 2020 the hottest September reading was 91°F (September 10, 2020).
Does it rain a lot in Seattle in September?
About 9 days in September have at least 0.01 in of precipitation, and the normal total is 1.7 in. The wettest September in 1991-2020 was in 2013 (5.0 in); the driest was in 1991 (0.02 in).
Is September a good time to visit Seattle?
September ranks 4th of 12 months on our comfort score for Seattle (80 out of 100). It has about 23 comfortable days. The best months are June, July and August.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and frost dates: Seattle Sand Pt WSFO (USW00094290), 6.6 mi NNE of the city center, 60 ft (113 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Seattle Boeing Fld (USW00024234), 5.4 mi SSE of the city center, 20 ft (153 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Seattle-Tacoma International Airport (727930-24233), 11 mi S of the city center, 369 ft (196 ft higher than the city). Hourly observations, 1991-2020.
- Not available for this location: cloud cover (no station close enough or similar enough in elevation).