Great Falls weather in September: Great Falls, Montana: normal highs, lows, rain and records for September
Great Falls in September has a normal high of 72°F and a normal low of 43°F, a daily mean of 57°F, falling from 78°F on the 1st to 65°F by the 30th. Measurable precipitation falls on 7 days in a normal September, 1.33 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 22°C and low of 6°C, 34 mm of precipitation and 2 cm of snow in September.
- NOAA stationGreat Falls Airport
- Station IDUSW00024143
- Location47.47°N 111.38°W
- Elevation3,664 ft (1,117 m)
- From the center4 miles
- Population60,013
- Jan 35° 15°
- Feb 37° 15°
- Mar 46° 22°
- Apr 55° 30°
- May 65° 38°
- Jun 73° 46°
- Jul 84° 51°
- Aug 83° 50°
- Sep 72° 43°
- Oct 57° 33°
- Nov 44° 24°
- Dec 36° 16°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Great Falls in September?
The normal high is 72°F and the normal low 43°F, for a daily mean of 57.2°F. September is 9.5°F cooler than August and 12.4°F warmer than October. September is the 4th warmest month of the year in Great Falls and the 4th wettest. Across the month the normal high falls 13°F, from 78°F on September 1 to 65°F on September 30. From one year to the next September's mean temperature typically moves about 3.0°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 54°F and 60°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 25%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 78°F | 47°F | 23% | 11% |
| September 8 | 75°F | 45°F | 24% | 11% |
| September 15 | 72°F | 43°F | 24% | 12% |
| September 22 | 69°F | 41°F | 25% | 11% |
| September 30 | 65°F | 39°F | 24% | 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 | 78°F | 47°F | 23% | 11% | 13 h 30 min |
| September 2 | 77°F | 46°F | 23% | 11% | 13 h 20 min |
| September 3 | 77°F | 46°F | 23% | 11% | 13 h 20 min |
| September 4 | 76°F | 46°F | 23% | 11% | 13 h 20 min |
| September 5 | 76°F | 46°F | 23% | 11% | 13 h 10 min |
| September 6 | 76°F | 45°F | 24% | 11% | 13 h 10 min |
| September 7 | 75°F | 45°F | 24% | 11% | 13 h 10 min |
| September 8 | 75°F | 45°F | 24% | 11% | 13 h |
| September 9 | 75°F | 45°F | 24% | 11% | 13 h |
| September 10 | 74°F | 44°F | 24% | 11% | 13 h |
| September 11 | 74°F | 44°F | 24% | 11% | 12 h 50 min |
| September 12 | 73°F | 44°F | 24% | 11% | 12 h 50 min |
| September 13 | 73°F | 44°F | 24% | 11% | 12 h 50 min |
| September 14 | 73°F | 43°F | 24% | 11% | 12 h 40 min |
| September 15 | 72°F | 43°F | 24% | 12% | 12 h 40 min |
| September 16 | 72°F | 43°F | 24% | 12% | 12 h 40 min |
| September 17 | 71°F | 43°F | 24% | 11% | 12 h 30 min |
| September 18 | 71°F | 42°F | 25% | 11% | 12 h 30 min |
| September 19 | 70°F | 42°F | 25% | 11% | 12 h 30 min |
| September 20 | 70°F | 42°F | 25% | 11% | 12 h 20 min |
| September 21 | 70°F | 41°F | 25% | 11% | 12 h 20 min |
| September 22 | 69°F | 41°F | 25% | 11% | 12 h 20 min |
| September 23 | 69°F | 41°F | 24% | 11% | 12 h 10 min |
| September 24 | 68°F | 41°F | 24% | 11% | 12 h 10 min |
| September 25 | 68°F | 40°F | 24% | 11% | 12 h 10 min |
| September 26 | 67°F | 40°F | 24% | 11% | 12 h |
| September 27 | 67°F | 40°F | 24% | 11% | 12 h |
| September 28 | 66°F | 39°F | 24% | 11% | 12 h |
| September 29 | 66°F | 39°F | 24% | 11% | 11 h 50 min |
| September 30 | 65°F | 39°F | 24% | 11% | 11 h 50 min |
- Normal high
- 72°FSeptember average
- Normal low
- 43°FSeptember average
- Precipitation
- 1.33 inmonth total
- Days with precipitation
- 70.01 inch or more
- Snowfall
- 0.8 inmonth total
- Days at 90°F or more
- 2
- Nights at 32°F or colder
- 2
- Daylight
- 13 h 30 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 18
- Days at 80°F or more
- 9
- Sunshine
- 78%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024143; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain or snow in Great Falls in September?
On a given September day the chance of 0.01 inch or more is 24% on average, highest around September 18 (25%). In all, 1.33 in falls on 7 days of a normal September.
In a normal September in Great Falls, 2 days reach 90°F, 2 nights fall to freezing and snowfall averages 0.8 inches.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024143.
How humid and windy is Great Falls in September?
At 3 p.m. the normal temperature is 63°F with 33% relative humidity and a dew point of 33°F; at 6 a.m. it is 44°F with 67% humidity. The wind averages 10.7 mph, most often from the west-southwest in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 44°F | 33°F | 67% | 9.7 mph | 70% |
| 9 a.m. | 52°F | 35°F | 52% | 11.7 mph | 70% |
| noon | 60°F | 34°F | 38% | 12.7 mph | 70% |
| 3 p.m. | 63°F | 33°F | 33% | 12.7 mph | 71% |
| 6 p.m. | 57°F | 34°F | 42% | 9.7 mph | 69% |
| 9 p.m. | 50°F | 34°F | 54% | 9.5 mph | 73% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024143. 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 Great Falls?
The warmest September temperature on Great Falls's official record (since 1891) is 102°F, on September 3, 2022; the coldest is 10°F, on September 24, 1926. The wettest September brought 3.56 in (1941); the snowiest, 19.3 inches (2019).
The September mean against the 1991-2020 normal of 57.2°F: 2021 59.8°F (+2.6), 2022 62.2°F (+5.0), 2023 60.3°F (+3.1), 2024 62.6°F (+5.4), 2025 63.5°F (+6.3), 2026 58.7°F (+1.5). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 59.8°F | +2.6°F | 0.26 in |
| 2022 | 62.2°F | +5.0°F | 2.33 in |
| 2023 | 60.3°F | +3.1°F | 2.52 in |
| 2024 | 62.6°F | +5.4°F | 1.80 in |
| 2025 | 63.5°F | +6.3°F | 0.28 in |
| 2026 | 58.7°F | +1.5°F | 1.00 in |
Source: records: ACIS, NWS threaded record GTFthr; recent months: ACIS, station USW00024143. Records and recent months use complete months only.
How does September in Great Falls compare across Montana?
Across the 141 places PlainClimate covers in Montana, September normal highs run from 62°F in Cooke City to 79°F in Hardin; Great Falls's is 72°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.