Seattle weather in September: Seattle, Washington: normal highs, lows, rain and records for September
Seattle in September has a normal high of 72°F and a normal low of 54°F, a daily mean of 63°F, falling from 75°F on the 1st to 67°F by the 30th. Measurable precipitation falls on 8 days in a normal September, 1.61 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 22°C and low of 12°C, 41 mm of precipitation in September.
- NOAA stationSeattle Tacoma International Airport
- Station IDUSW00024233
- Location47.44°N 122.31°W
- Elevation370 ft (113 m)
- From the center12 miles
- Population780,995
- Jan 48° 38°
- Feb 50° 38°
- Mar 54° 40°
- Apr 59° 43°
- May 66° 49°
- Jun 71° 53°
- Jul 77° 57°
- Aug 78° 57°
- Sep 72° 54°
- Oct 61° 47°
- Nov 52° 41°
- Dec 47° 37°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Seattle in September?
The normal high is 72°F and the normal low 54°F, for a daily mean of 62.6°F. September is 4.8°F cooler than August and 8.8°F warmer than October. September is the 3rd warmest month of the year in Seattle and the 9th wettest. Across the month the normal high falls 8°F, from 75°F on September 1 to 67°F on September 30. From one year to the next September's mean temperature typically moves about 1.6°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 61°F and 64°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 36%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 75°F | 56°F | 22% | 11% |
| September 8 | 74°F | 55°F | 25% | 12% |
| September 15 | 72°F | 54°F | 29% | 14% |
| September 22 | 70°F | 53°F | 32% | 16% |
| September 30 | 67°F | 51°F | 36% | 19% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 75°F | 56°F | 22% | 11% | 13 h 30 min |
| September 2 | 75°F | 56°F | 22% | 11% | 13 h 20 min |
| September 3 | 75°F | 56°F | 23% | 11% | 13 h 20 min |
| September 4 | 75°F | 56°F | 23% | 11% | 13 h 20 min |
| September 5 | 75°F | 55°F | 24% | 12% | 13 h 10 min |
| September 6 | 74°F | 55°F | 24% | 12% | 13 h 10 min |
| September 7 | 74°F | 55°F | 25% | 12% | 13 h 10 min |
| September 8 | 74°F | 55°F | 25% | 12% | 13 h |
| September 9 | 74°F | 55°F | 25% | 13% | 13 h |
| September 10 | 74°F | 55°F | 26% | 13% | 13 h |
| September 11 | 73°F | 55°F | 26% | 13% | 12 h 50 min |
| September 12 | 73°F | 54°F | 27% | 13% | 12 h 50 min |
| September 13 | 73°F | 54°F | 28% | 14% | 12 h 50 min |
| September 14 | 72°F | 54°F | 28% | 14% | 12 h 40 min |
| September 15 | 72°F | 54°F | 29% | 14% | 12 h 40 min |
| September 16 | 72°F | 54°F | 29% | 15% | 12 h 40 min |
| September 17 | 72°F | 54°F | 30% | 15% | 12 h 30 min |
| September 18 | 71°F | 53°F | 30% | 15% | 12 h 30 min |
| September 19 | 71°F | 53°F | 31% | 15% | 12 h 30 min |
| September 20 | 71°F | 53°F | 31% | 16% | 12 h 20 min |
| September 21 | 70°F | 53°F | 32% | 16% | 12 h 20 min |
| September 22 | 70°F | 53°F | 32% | 16% | 12 h 20 min |
| September 23 | 69°F | 52°F | 33% | 17% | 12 h 10 min |
| September 24 | 69°F | 52°F | 33% | 17% | 12 h 10 min |
| September 25 | 69°F | 52°F | 34% | 17% | 12 h 10 min |
| September 26 | 68°F | 52°F | 34% | 18% | 12 h |
| September 27 | 68°F | 51°F | 35% | 18% | 12 h |
| September 28 | 68°F | 51°F | 35% | 18% | 12 h |
| September 29 | 67°F | 51°F | 36% | 19% | 11 h 50 min |
| September 30 | 67°F | 51°F | 36% | 19% | 11 h 50 min |
- Normal high
- 72°FSeptember average
- Normal low
- 54°FSeptember average
- Precipitation
- 1.61 inmonth total
- Days with precipitation
- 80.01 inch or more
- Daylight
- 13 h 30 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 16
- Days at 80°F or more
- 4
- Sunshine
- 74%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024233; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Seattle in September?
On a given September day the chance of 0.01 inch or more is 29% on average, highest around September 30 (36%). In all, 1.61 in falls on 8 days of a normal September.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024233.
How humid and windy is Seattle in September?
At 3 p.m. the normal temperature is 65°F with 57% relative humidity and a dew point of 49°F; at 6 a.m. it is 52°F with 88% humidity. The wind averages 6.8 mph, most often from the west in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 52°F | 49°F | 88% | 5.9 mph | – |
| 9 a.m. | 56°F | 50°F | 79% | 6.7 mph | – |
| noon | 62°F | 50°F | 65% | 7.9 mph | 33% |
| 3 p.m. | 65°F | 49°F | 57% | 8.5 mph | 32% |
| 6 p.m. | 60°F | 49°F | 66% | 6.5 mph | 32% |
| 9 p.m. | 57°F | 49°F | 75% | 6.8 mph | 47% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024233. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for September in Seattle?
The warmest September temperature on this station's record (since 1945) is 98°F, on September 2, 1988; the coldest is 35°F, on September 27, 1972. The wettest September brought 6.17 in (2013).
The September mean against the 1991-2020 normal of 62.6°F: 2021 61.9°F (−0.7), 2022 64.8°F (+2.2), 2023 62.0°F (−0.6), 2024 62.6°F (at normal), 2025 64.1°F (+1.5), 2026 60.3°F (−2.3). 2 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 61.9°F | −0.7°F | 3.02 in |
| 2022 | 64.8°F | +2.2°F | 0.25 in |
| 2023 | 62.0°F | −0.6°F | 3.44 in |
| 2024 | 62.6°F | at normal | 0.62 in |
| 2025 | 64.1°F | +1.5°F | 0.76 in |
| 2026 | 60.3°F | −2.3°F | 1.46 in |
Source: records: ACIS, station USW00024233; recent months: ACIS, station USW00024233. Records and recent months use complete months only.
How does September in Seattle compare across Washington?
Across the 96 places PlainClimate covers in Washington, September normal highs run from 66°F in Coupeville to 81°F in Pasco; Seattle's is 72°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.