Rapid City weather in September: Rapid City, South Dakota: normal highs, lows, rain and records for September
Rapid City in September has a normal high of 76°F and a normal low of 46°F, a daily mean of 61°F, falling from 82°F on the 1st to 69°F by the 30th. Measurable precipitation falls on 7 days in a normal September, 1.22 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 24°C and low of 8°C, 31 mm of precipitation and 0 cm of snow in September.
- NOAA stationRapid City Regional Airport
- Station IDUSW00024090
- Location44.04°N 103.05°W
- Elevation3,160 ft (963 m)
- Population79,894
- Jan 36° 13°
- Feb 38° 14°
- Mar 48° 23°
- Apr 57° 31°
- May 67° 42°
- Jun 78° 52°
- Jul 86° 59°
- Aug 85° 56°
- Sep 76° 46°
- Oct 60° 34°
- Nov 47° 22°
- Dec 37° 14°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Rapid City in September?
The normal high is 76°F and the normal low 46°F, for a daily mean of 61.3°F. September is 9.5°F cooler than August and 14.2°F warmer than October. September is the 4th warmest month of the year in Rapid City and the 7th wettest. Across the month the normal high falls 13°F, from 82°F on September 1 to 69°F on September 30. From one year to the next September's mean temperature typically moves about 2.7°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 59°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 23%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 82°F | 52°F | 23% | 10% |
| September 8 | 80°F | 49°F | 22% | 10% |
| September 15 | 77°F | 47°F | 22% | 10% |
| September 22 | 73°F | 44°F | 23% | 10% |
| September 30 | 69°F | 41°F | 23% | 11% |
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 | 82°F | 52°F | 23% | 10% | 13 h 20 min |
| September 2 | 82°F | 51°F | 23% | 10% | 13 h 10 min |
| September 3 | 81°F | 51°F | 22% | 10% | 13 h 10 min |
| September 4 | 81°F | 51°F | 22% | 10% | 13 h 10 min |
| September 5 | 81°F | 50°F | 22% | 10% | 13 h |
| September 6 | 80°F | 50°F | 22% | 10% | 13 h |
| September 7 | 80°F | 50°F | 22% | 10% | 13 h |
| September 8 | 80°F | 49°F | 22% | 10% | 13 h |
| September 9 | 79°F | 49°F | 22% | 10% | 12 h 50 min |
| September 10 | 79°F | 49°F | 22% | 10% | 12 h 50 min |
| September 11 | 79°F | 48°F | 22% | 10% | 12 h 50 min |
| September 12 | 78°F | 48°F | 22% | 10% | 12 h 40 min |
| September 13 | 78°F | 48°F | 22% | 10% | 12 h 40 min |
| September 14 | 77°F | 47°F | 22% | 10% | 12 h 40 min |
| September 15 | 77°F | 47°F | 22% | 10% | 12 h 40 min |
| September 16 | 76°F | 46°F | 22% | 10% | 12 h 30 min |
| September 17 | 76°F | 46°F | 22% | 10% | 12 h 30 min |
| September 18 | 75°F | 46°F | 23% | 10% | 12 h 30 min |
| September 19 | 75°F | 45°F | 23% | 10% | 12 h 20 min |
| September 20 | 74°F | 45°F | 23% | 10% | 12 h 20 min |
| September 21 | 74°F | 44°F | 23% | 10% | 12 h 20 min |
| September 22 | 73°F | 44°F | 23% | 10% | 12 h 10 min |
| September 23 | 73°F | 44°F | 23% | 11% | 12 h 10 min |
| September 24 | 72°F | 43°F | 23% | 11% | 12 h 10 min |
| September 25 | 72°F | 43°F | 23% | 11% | 12 h 10 min |
| September 26 | 71°F | 42°F | 23% | 11% | 12 h |
| September 27 | 71°F | 42°F | 23% | 11% | 12 h |
| September 28 | 70°F | 42°F | 23% | 11% | 12 h |
| September 29 | 69°F | 41°F | 23% | 11% | 11 h 50 min |
| September 30 | 69°F | 41°F | 23% | 11% | 11 h 50 min |
- Normal high
- 76°FSeptember average
- Normal low
- 46°FSeptember average
- Precipitation
- 1.22 inmonth total
- Days with precipitation
- 70.01 inch or more
- Snowfall
- 0.1 inmonth total
- Days at 90°F or more
- 4
- Nights at 32°F or colder
- 1
- Daylight
- 13 h 20 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 22
- Days at 80°F or more
- 13
- Sunshine
- 82%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024090; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain or snow in Rapid City in September?
On a given September day the chance of 0.01 inch or more is 22% on average, highest around September 1 (23%). In all, 1.22 in falls on 7 days of a normal September.
In a normal September in Rapid City, 4 days reach 90°F, 1 nights fall to freezing and snowfall averages 0.1 inches.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024090.
How humid and windy is Rapid City in September?
At 3 p.m. the normal temperature is 67°F with 33% relative humidity and a dew point of 37°F; at 6 a.m. it is 45°F with 71% humidity. The wind averages 10.3 mph, most often from the north-northwest in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 45°F | 36°F | 71% | 8.4 mph | 75% |
| 9 a.m. | 58°F | 39°F | 49% | 11.7 mph | 75% |
| noon | 65°F | 38°F | 36% | 13.5 mph | 75% |
| 3 p.m. | 67°F | 37°F | 33% | 13.9 mph | 77% |
| 6 p.m. | 57°F | 38°F | 48% | 9.6 mph | 76% |
| 9 p.m. | 51°F | 38°F | 61% | 8.0 mph | 76% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024090. 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 Rapid City?
The warmest September temperature on Rapid City's official record (since 1942) is 104°F, on September 4, 1960; the coldest is 18°F, on September 26, 1942. The wettest September brought 3.94 in (1946); the snowiest, 2.0 inches (1970).
The September mean against the 1991-2020 normal of 61.3°F: 2021 65.0°F (+3.8), 2022 65.4°F (+4.1), 2023 64.5°F (+3.2), 2024 70.0°F (+8.7), 2025 66.5°F (+5.2), 2026 66.2°F (+4.9). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 65.0°F | +3.8°F | 0.71 in |
| 2022 | 65.4°F | +4.1°F | 0.39 in |
| 2023 | 64.5°F | +3.2°F | 0.99 in |
| 2024 | 70.0°F | +8.7°F | 1.18 in |
| 2025 | 66.5°F | +5.2°F | 1.05 in |
| 2026 | 66.2°F | +4.9°F | 1.53 in |
Source: records: ACIS, NWS threaded record RAPthr; recent months: ACIS, station USW00024090. Records and recent months use complete months only.
How does September in Rapid City compare across South Dakota?
Across the 100 places PlainClimate covers in South Dakota, September normal highs run from 69°F in Custer to 82°F in Interior; Rapid City's is 76°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- Rapid City in August85°F by day, 56°F at night
- Rapid City in October60°F by day, 34°F at night
- Rapid City through the yearEvery month, frost dates, records and recent years
- South Dakota in SeptemberThe statewide normal and the warmest and coolest places
- Interior: South Dakota's warmest Septembernormal high 82°F