Washington weather in September: Washington, District of Columbia: normal highs, lows, rain and records for September
Washington in September has a normal high of 81°F and a normal low of 64°F, a daily mean of 72°F, falling from 85°F on the 1st to 75°F by the 30th. Measurable precipitation falls on 9 days in a normal September, 3.93 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 27°C and low of 18°C, 100 mm of precipitation in September.
- NOAA stationWashington Reagan Airport
- Station IDUSW00013743
- Location38.85°N 77.03°W
- Elevation10 ft (3 m)
- From the center4 miles
- Population702,250
- Jan 45° 30°
- Feb 48° 32°
- Mar 57° 39°
- Apr 68° 48°
- May 77° 58°
- Jun 85° 68°
- Jul 90° 72°
- Aug 88° 71°
- Sep 81° 64°
- Oct 69° 52°
- Nov 58° 42°
- Dec 49° 35°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Washington in September?
The normal high is 81°F and the normal low 64°F, for a daily mean of 72.4°F. September is 7.0°F cooler than August and 11.6°F warmer than October. September is the 4th warmest month of the year in Washington and the 4th wettest. Across the month the normal high falls 10°F, from 85°F on September 1 to 75°F on September 30. From one year to the next September's mean temperature typically moves about 2.3°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 70°F and 75°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 28%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 85°F | 69°F | 27% | 18% |
| September 8 | 83°F | 67°F | 27% | 18% |
| September 15 | 81°F | 65°F | 27% | 18% |
| September 22 | 79°F | 62°F | 28% | 18% |
| September 30 | 75°F | 59°F | 28% | 17% |
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 | 85°F | 69°F | 27% | 18% | 13 h |
| September 2 | 85°F | 68°F | 27% | 18% | 13 h |
| September 3 | 85°F | 68°F | 27% | 18% | 13 h |
| September 4 | 85°F | 68°F | 27% | 18% | 13 h |
| September 5 | 84°F | 68°F | 27% | 18% | 12 h 50 min |
| September 6 | 84°F | 67°F | 27% | 18% | 12 h 50 min |
| September 7 | 84°F | 67°F | 27% | 18% | 12 h 50 min |
| September 8 | 83°F | 67°F | 27% | 18% | 12 h 50 min |
| September 9 | 83°F | 67°F | 27% | 18% | 12 h 50 min |
| September 10 | 83°F | 66°F | 27% | 18% | 12 h 40 min |
| September 11 | 82°F | 66°F | 27% | 18% | 12 h 40 min |
| September 12 | 82°F | 66°F | 27% | 18% | 12 h 40 min |
| September 13 | 82°F | 65°F | 27% | 18% | 12 h 40 min |
| September 14 | 81°F | 65°F | 27% | 18% | 12 h 30 min |
| September 15 | 81°F | 65°F | 27% | 18% | 12 h 30 min |
| September 16 | 81°F | 64°F | 27% | 18% | 12 h 30 min |
| September 17 | 80°F | 64°F | 28% | 18% | 12 h 30 min |
| September 18 | 80°F | 63°F | 28% | 18% | 12 h 20 min |
| September 19 | 80°F | 63°F | 28% | 18% | 12 h 20 min |
| September 20 | 79°F | 63°F | 28% | 18% | 12 h 20 min |
| September 21 | 79°F | 62°F | 28% | 18% | 12 h 20 min |
| September 22 | 79°F | 62°F | 28% | 18% | 12 h 10 min |
| September 23 | 78°F | 62°F | 28% | 18% | 12 h 10 min |
| September 24 | 78°F | 61°F | 28% | 18% | 12 h 10 min |
| September 25 | 77°F | 61°F | 28% | 18% | 12 h 10 min |
| September 26 | 77°F | 60°F | 28% | 18% | 12 h |
| September 27 | 77°F | 60°F | 28% | 18% | 12 h |
| September 28 | 76°F | 60°F | 28% | 18% | 12 h |
| September 29 | 76°F | 59°F | 28% | 17% | 12 h |
| September 30 | 75°F | 59°F | 28% | 17% | 11 h 50 min |
- Normal high
- 81°FSeptember average
- Normal low
- 64°FSeptember average
- Precipitation
- 3.93 inmonth total
- Days with precipitation
- 90.01 inch or more
- Days at 90°F or more
- 4
- Daylight
- 13 h to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 28
- Days at 80°F or more
- 17
- Sunshine
- 76%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00013743; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Washington in September?
On a given September day the chance of 0.01 inch or more is 27% on average, highest around September 25 (28%). In all, 3.93 in falls on 9 days of a normal September, 1 of them with an inch or more.
In a normal September in Washington, 4 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00013743.
How humid and windy is Washington in September?
At 3 p.m. the normal temperature is 73°F with 53% relative humidity and a dew point of 55°F; at 6 a.m. it is 61°F with 82% humidity. The wind averages 8.0 mph, most often from the west-southwest in the afternoon.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 61°F | 55°F | 82% | 6.9 mph | 39% |
| 9 a.m. | 66°F | 56°F | 70% | 8.6 mph | 35% |
| noon | 71°F | 55°F | 57% | 9.3 mph | 30% |
| 3 p.m. | 73°F | 55°F | 53% | 9.9 mph | 27% |
| 6 p.m. | 69°F | 55°F | 61% | 8.7 mph | 36% |
| 9 p.m. | 65°F | 56°F | 72% | 7.2 mph | 49% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00013743. 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 Washington?
The warmest September temperature on Washington's official record (since 1871) is 104°F, on September 7, 1881; the coldest is 36°F, on September 23, 1904. The wettest September brought 17.45 in (1934).
The September mean against the 1991-2020 normal of 72.4°F: 2021 73.2°F (+0.8), 2022 72.7°F (+0.3), 2023 73.4°F (+1.0), 2024 72.5°F (+0.1), 2025 72.2°F (−0.2), 2026 73.5°F (+1.1). 5 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 73.2°F | +0.8°F | 4.03 in |
| 2022 | 72.7°F | +0.3°F | 2.27 in |
| 2023 | 73.4°F | +1.0°F | 3.60 in |
| 2024 | 72.5°F | +0.1°F | 2.31 in |
| 2025 | 72.2°F | −0.2°F | 3.72 in |
| 2026 | 73.5°F | +1.1°F | 4.26 in |
Source: records: ACIS, NWS threaded record DCAthr; recent months: ACIS, station USW00013743. Records and recent months use complete months only.
How does September in Washington compare across District of Columbia?
Across the 1 places PlainClimate covers in District of Columbia, September normal highs run from 81°F in Washington to 81°F in Washington; Washington's is 81°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.