Helena weather in September: Helena, Montana: normal highs, lows, rain and records for September
Helena in September has a normal high of 73°F and a normal low of 45°F, a daily mean of 59°F, falling from 79°F on the 1st to 67°F by the 30th. Measurable precipitation falls on 6 days in a normal September, 0.96 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 23°C and low of 7°C, 24 mm of precipitation and 1 cm of snow in September.
- NOAA stationHelena Regional Airport
- Station IDUSW00024144
- Location46.61°N 111.96°W
- Elevation3,828 ft (1,167 m)
- From the center3 miles
- Population34,729
- Jan 32° 14°
- Feb 37° 17°
- Mar 48° 25°
- Apr 57° 32°
- May 66° 42°
- Jun 75° 49°
- Jul 86° 55°
- Aug 85° 53°
- Sep 73° 45°
- Oct 58° 34°
- Nov 43° 23°
- Dec 33° 14°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Helena in September?
The normal high is 73°F and the normal low 45°F, for a daily mean of 58.9°F. September is 9.9°F cooler than August and 13.4°F warmer than October. September is the 4th warmest month of the year in Helena and the 6th wettest. Across the month the normal high falls 12°F, from 79°F on September 1 to 67°F on September 30. From one year to the next September's mean temperature typically moves about 2.6°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 56°F and 62°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 20%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 79°F | 49°F | 20% | 10% |
| September 8 | 77°F | 47°F | 20% | 9% |
| September 15 | 74°F | 45°F | 20% | 9% |
| September 22 | 71°F | 43°F | 20% | 9% |
| September 30 | 67°F | 40°F | 20% | 9% |
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 | 79°F | 49°F | 20% | 10% | 13 h 20 min |
| September 2 | 79°F | 48°F | 20% | 10% | 13 h 20 min |
| September 3 | 78°F | 48°F | 20% | 10% | 13 h 20 min |
| September 4 | 78°F | 48°F | 20% | 10% | 13 h 10 min |
| September 5 | 78°F | 48°F | 20% | 9% | 13 h 10 min |
| September 6 | 77°F | 47°F | 20% | 9% | 13 h 10 min |
| September 7 | 77°F | 47°F | 20% | 9% | 13 h |
| September 8 | 77°F | 47°F | 20% | 9% | 13 h |
| September 9 | 76°F | 47°F | 20% | 9% | 13 h |
| September 10 | 76°F | 46°F | 20% | 9% | 12 h 50 min |
| September 11 | 75°F | 46°F | 20% | 9% | 12 h 50 min |
| September 12 | 75°F | 46°F | 20% | 9% | 12 h 50 min |
| September 13 | 75°F | 46°F | 20% | 9% | 12 h 40 min |
| September 14 | 74°F | 45°F | 20% | 9% | 12 h 40 min |
| September 15 | 74°F | 45°F | 20% | 9% | 12 h 40 min |
| September 16 | 73°F | 45°F | 20% | 9% | 12 h 30 min |
| September 17 | 73°F | 44°F | 20% | 9% | 12 h 30 min |
| September 18 | 73°F | 44°F | 20% | 9% | 12 h 30 min |
| September 19 | 72°F | 44°F | 20% | 9% | 12 h 20 min |
| September 20 | 72°F | 43°F | 20% | 9% | 12 h 20 min |
| September 21 | 71°F | 43°F | 20% | 9% | 12 h 20 min |
| September 22 | 71°F | 43°F | 20% | 9% | 12 h 20 min |
| September 23 | 70°F | 43°F | 20% | 9% | 12 h 10 min |
| September 24 | 70°F | 42°F | 20% | 9% | 12 h 10 min |
| September 25 | 69°F | 42°F | 20% | 9% | 12 h 10 min |
| September 26 | 69°F | 42°F | 20% | 9% | 12 h |
| September 27 | 68°F | 41°F | 20% | 9% | 12 h |
| September 28 | 68°F | 41°F | 20% | 9% | 12 h |
| September 29 | 67°F | 40°F | 20% | 9% | 11 h 50 min |
| September 30 | 67°F | 40°F | 20% | 9% | 11 h 50 min |
- Normal high
- 73°FSeptember average
- Normal low
- 45°FSeptember average
- Precipitation
- 0.96 inmonth total
- Days with precipitation
- 60.01 inch or more
- Snowfall
- 0.2 inmonth total
- Days at 90°F or more
- 2
- Nights at 32°F or colder
- 2
- Daylight
- 13 h 20 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 19
- Days at 80°F or more
- 10
- Sunshine
- 78%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024144; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain or snow in Helena in September?
On a given September day the chance of 0.01 inch or more is 20% on average, highest around September 30 (20%). In all, 0.96 in falls on 6 days of a normal September.
In a normal September in Helena, 2 days reach 90°F, 2 nights fall to freezing and snowfall averages 0.2 inches.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024144.
How humid and windy is Helena in September?
At 3 p.m. the normal temperature is 64°F with 32% relative humidity and a dew point of 34°F; at 6 a.m. it is 42°F with 69% humidity. The wind averages 6.2 mph, most often from the west-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. | 42°F | 33°F | 69% | 3.9 mph | 68% |
| 9 a.m. | 49°F | 35°F | 59% | 4.3 mph | 70% |
| noon | 59°F | 35°F | 40% | 7.9 mph | 70% |
| 3 p.m. | 64°F | 34°F | 32% | 9.8 mph | 71% |
| 6 p.m. | 60°F | 34°F | 38% | 7.5 mph | 70% |
| 9 p.m. | 52°F | 34°F | 50% | 6.0 mph | 72% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024144. 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 Helena?
The warmest September temperature on Helena's official record (since 1880) is 102°F, on September 7, 2022; the coldest is 6°F, on September 24, 1926. The wettest September brought 3.66 in (1882); the snowiest, 14.2 inches (1925).
The September mean against the 1991-2020 normal of 58.9°F: 2021 62.2°F (+3.3), 2022 64.2°F (+5.3), 2023 61.9°F (+3.0), 2024 64.3°F (+5.4), 2025 63.5°F (+4.6), 2026 59.9°F (+1.0). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 62.2°F | +3.3°F | 0.03 in |
| 2022 | 64.2°F | +5.3°F | 1.95 in |
| 2023 | 61.9°F | +3.0°F | 2.70 in |
| 2024 | 64.3°F | +5.4°F | 1.23 in |
| 2025 | 63.5°F | +4.6°F | 0.60 in |
| 2026 | 59.9°F | +1.0°F | 1.38 in |
Source: records: ACIS, NWS threaded record HLNthr; recent months: ACIS, station USW00024144. Records and recent months use complete months only.
How does September in Helena 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; Helena's is 73°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.