Lewistown weather in September: Lewistown, Montana: normal highs, lows, rain and records for September
Lewistown in September has a normal high of 70°F and a normal low of 42°F, a daily mean of 56°F, falling from 76°F on the 1st to 64°F by the 30th. Measurable precipitation falls on 9 days in a normal September, 1.39 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 21°C and low of 5°C, 35 mm of precipitation in September.
- NOAA stationLewistown Municipal Airport
- Station IDUSW00024036
- Location47.05°N 109.46°W
- Elevation4,145 ft (1,263 m)
- Population6,204
- Jan 34° 13°
- Feb 35° 14°
- Mar 44° 21°
- Apr 53° 29°
- May 63° 37°
- Jun 71° 45°
- Jul 82° 51°
- Aug 81° 50°
- Sep 70° 42°
- Oct 56° 31°
- Nov 43° 21°
- Dec 35° 14°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Lewistown in September?
The normal high is 70°F and the normal low 42°F, for a daily mean of 55.9°F. September is 9.5°F cooler than August and 12.5°F warmer than October. September is the 4th warmest month of the year in Lewistown and the 6th wettest. Across the month the normal high falls 12°F, from 76°F on September 1 to 64°F on September 30. From one year to the next September's mean temperature typically moves about 2.8°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 53°F and 59°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 31%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 76°F | 46°F | 28% | 13% |
| September 8 | 74°F | 44°F | 28% | 14% |
| September 15 | 71°F | 42°F | 29% | 14% |
| September 22 | 68°F | 40°F | 30% | 15% |
| September 30 | 64°F | 37°F | 31% | 14% |
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 | 76°F | 46°F | 28% | 13% | 13 h 20 min |
| September 2 | 76°F | 45°F | 28% | 13% | 13 h 20 min |
| September 3 | 76°F | 45°F | 28% | 13% | 13 h 20 min |
| September 4 | 75°F | 45°F | 28% | 13% | 13 h 10 min |
| September 5 | 75°F | 45°F | 28% | 13% | 13 h 10 min |
| September 6 | 74°F | 44°F | 28% | 14% | 13 h 10 min |
| September 7 | 74°F | 44°F | 28% | 14% | 13 h 10 min |
| September 8 | 74°F | 44°F | 28% | 14% | 13 h |
| September 9 | 73°F | 44°F | 28% | 14% | 13 h |
| September 10 | 73°F | 43°F | 28% | 14% | 13 h |
| September 11 | 73°F | 43°F | 28% | 14% | 12 h 50 min |
| September 12 | 72°F | 43°F | 29% | 14% | 12 h 50 min |
| September 13 | 72°F | 42°F | 29% | 14% | 12 h 50 min |
| September 14 | 71°F | 42°F | 29% | 14% | 12 h 40 min |
| September 15 | 71°F | 42°F | 29% | 14% | 12 h 40 min |
| September 16 | 70°F | 42°F | 29% | 15% | 12 h 40 min |
| September 17 | 70°F | 41°F | 29% | 15% | 12 h 30 min |
| September 18 | 70°F | 41°F | 30% | 15% | 12 h 30 min |
| September 19 | 69°F | 41°F | 30% | 15% | 12 h 30 min |
| September 20 | 69°F | 40°F | 30% | 15% | 12 h 20 min |
| September 21 | 68°F | 40°F | 30% | 15% | 12 h 20 min |
| September 22 | 68°F | 40°F | 30% | 15% | 12 h 20 min |
| September 23 | 67°F | 39°F | 30% | 15% | 12 h 10 min |
| September 24 | 67°F | 39°F | 30% | 15% | 12 h 10 min |
| September 25 | 66°F | 39°F | 30% | 15% | 12 h 10 min |
| September 26 | 66°F | 38°F | 30% | 15% | 12 h |
| September 27 | 65°F | 38°F | 30% | 14% | 12 h |
| September 28 | 65°F | 38°F | 30% | 14% | 12 h |
| September 29 | 64°F | 37°F | 30% | 14% | 11 h 50 min |
| September 30 | 64°F | 37°F | 31% | 14% | 11 h 50 min |
- Normal high
- 70°FSeptember average
- Normal low
- 42°FSeptember average
- Precipitation
- 1.39 inmonth total
- Days with precipitation
- 90.01 inch or more
- Days at 90°F or more
- 1
- Nights at 32°F or colder
- 3
- Daylight
- 13 h 20 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 16
- Days at 80°F or more
- 7
- Sunshine
- 79%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024036; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Lewistown in September?
On a given September day the chance of 0.01 inch or more is 29% on average, highest around September 30 (31%). In all, 1.39 in falls on 9 days of a normal September.
In a normal September in Lewistown, 1 days reach 90°F and 3 nights fall to freezing.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024036.
How humid and windy is Lewistown in September?
At 3 p.m. the normal temperature is 61°F with 34% relative humidity and a dew point of 32°F; at 6 a.m. it is 41°F with 69% humidity. The wind averages 8.4 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. | 41°F | 32°F | 69% | 7.4 mph | – |
| 9 a.m. | 52°F | 34°F | 51% | 8.0 mph | – |
| noon | 59°F | 33°F | 37% | 10.4 mph | – |
| 3 p.m. | 61°F | 32°F | 34% | 10.9 mph | – |
| 6 p.m. | 55°F | 34°F | 45% | 7.7 mph | – |
| 9 p.m. | 47°F | 34°F | 59% | 8.4 mph | – |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024036. 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 Lewistown?
The warmest September temperature on this station's record (since 1896) is 100°F, on September 7, 2022; the coldest is 6°F, on September 24, 1926. The wettest September brought 6.07 in (2024); the snowiest, 10.0 inches (1954).
The September mean against the 1991-2020 normal of 55.9°F: 2021 58.5°F (+2.6), 2022 61.5°F (+5.6), 2023 58.9°F (+3.0), 2024 61.6°F (+5.7), 2025 60.8°F (+4.9), 2026 57.9°F (+2.0). 6 of 6 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 58.5°F | +2.6°F | 0.07 in |
| 2022 | 61.5°F | +5.6°F | 2.38 in |
| 2023 | 58.9°F | +3.0°F | 3.28 in |
| 2024 | 61.6°F | +5.7°F | 6.07 in |
| 2025 | 60.8°F | +4.9°F | 0.95 in |
| 2026 | 57.9°F | +2.0°F | 0.94 in |
Source: records: ACIS, station USW00024036; recent months: ACIS, station USW00024036. Records and recent months use complete months only.
How does September in Lewistown 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; Lewistown's is 70°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.