Lewistown Weather in September
Average highs run from 76°F on September 1 to 64°F on September 30, and lows from 46°F to 37°F. Normal precipitation for the month is 1.39 in over about 9 wet days.
September day by day
The normal high and low for each date, and the record, in °F.
- Normal low
- Normal high
- Record high
- Record low
September at a glance
- Average high
- 70°F
- Average low
- 42°F
- Precipitation
- 1.39 in
- Snowfall
- 2.1 in
- Record high
- 100°FSep 7, 2022
- Record low
- 6°FSep 24, 1926
- Chance of a freeze
- 83%
- Days of 90°F or more
- 1.3
- Daylight
- 13 h 20 min to 11 h 44 min
- Cloud cover
- 53%
- Humidity
- 57%
- Dew point
- 37°F
- Wind
- 9.6 mph
Every day of the month
A wet day has at least 0.01 inch of precipitation; snow means at least 0.1 inch of snowfall.
| Date | Normal high | Normal low | Record high | Record low | Chance wet | Chance of snow |
|---|---|---|---|---|---|---|
| Sep 1 | 76°F | 46°F | 97°F 1983 | 26°F 1930 | 28% | 1% |
| Sep 2 | 76°F | 45°F | 96°F 1945 | 29°F 1900 | 28% | 1% |
| Sep 3 | 76°F | 45°F | 97°F 2022 | 29°F 1929 | 28% | 1% |
| Sep 4 | 75°F | 45°F | 93°F 1924 | 20°F 1929 | 28% | 1% |
| Sep 5 | 75°F | 45°F | 97°F 2020 | 28°F 1956 | 28% | 1% |
| Sep 6 | 74°F | 44°F | 94°F 1908 | 21°F 1929 | 28% | 2% |
| Sep 7 | 74°F | 44°F | 100°F 2022 | 18°F 1929 | 28% | 2% |
| Sep 8 | 74°F | 44°F | 95°F 1979 | 19°F 1929 | 28% | 2% |
| Sep 9 | 73°F | 44°F | 99°F 1909 | 13°F 1896 | 28% | 2% |
| Sep 10 | 73°F | 43°F | 91°F 1966 | 16°F 1896 | 28% | 2% |
| Sep 11 | 73°F | 43°F | 98°F 1908 | 11°F 1921 | 28% | 2% |
| Sep 12 | 72°F | 43°F | 91°F 1953 | 22°F 1921 | 29% | 3% |
| Sep 13 | 72°F | 42°F | 90°F 1959 | 23°F 1896 | 29% | 3% |
| Sep 14 | 71°F | 42°F | 94°F 1948 | 19°F 1970 | 29% | 3% |
| Sep 15 | 71°F | 42°F | 93°F 1908 | 23°F 1916 | 29% | 3% |
| Sep 16 | 70°F | 42°F | 91°F 1998 | 22°F 1912 | 29% | 3% |
| Sep 17 | 70°F | 41°F | 91°F 2009 | 23°F 1902 | 29% | 4% |
| Sep 18 | 70°F | 41°F | 90°F 1966 | 19°F 1965 | 30% | 4% |
| Sep 19 | 69°F | 41°F | 92°F 1938 | 22°F 1943 | 30% | 4% |
| Sep 20 | 69°F | 40°F | 92°F 1922 | 18°F 1983 | 30% | 4% |
| Sep 21 | 68°F | 40°F | 92°F 1938 | 19°F 1995 | 30% | 4% |
| Sep 22 | 68°F | 40°F | 95°F 1905 | 23°F 2000 | 30% | 5% |
| Sep 23 | 67°F | 39°F | 90°F 1966 | 18°F 1926 | 30% | 5% |
| Sep 24 | 67°F | 39°F | 89°F 1922 | 6°F 1926 | 30% | 5% |
| Sep 25 | 66°F | 39°F | 92°F 1922 | 13°F 1926 | 30% | 5% |
| Sep 26 | 66°F | 38°F | 90°F 2015 | 9°F 1900 | 30% | 6% |
| Sep 27 | 65°F | 38°F | 88°F 1963 | 17°F 1900 | 30% | 6% |
| Sep 28 | 65°F | 38°F | 87°F 1909 | 17°F 1984 | 30% | 6% |
| Sep 29 | 64°F | 37°F | 89°F 1967 | 19°F 2019 | 30% | 6% |
| Sep 30 | 64°F | 37°F | 93°F 1906 | 17°F 1985 | 31% | 7% |
Chance of rain
- Chance of a wet day
- Chance of snowfall
Sunrise and sunset
Times for 2026, local time (MDT).
- September 1
- sunrise 6:37 AM, sunset 7:57 PM
- September 30
- sunrise 7:15 AM, sunset 6:59 PM
Other months
Sources
Normals: NOAA NCEI U.S. Climate Normals, 1991-2020, station USW00024036 (Lewistown Muni AP), public domain. Records: NOAA GHCN-Daily, station USW00024036, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-25. Sun and moon: computed with the NOAA solar equations and Meeus.