September weather in Westby, MT
The average temperature in Westby in September is 55.4°F (41.1°F–69.6°F). Average precipitation: 1.26 inches.
September is a fall month in Westby, and is warmer than the annual average of 39.1°F. Daily temperatures swing about 28.5°F between overnight low and afternoon high. Daylight averages about 12h 20m. For travel, September is a comfortable month to visit.
Avg High
69.6°F
Avg Low
41.1°F
Precipitation
1.26 in
Daylight
12h 20m
September records in Westby
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 102.9°F (1983) | 35.1°F (1974) | 0.94 in (1979) |
| September 2 | 99.0°F (1983) | 30.0°F (1974) | 1.07 in (1973) |
| September 3 | 102.9°F (1940) | 28.9°F (1958) | 1.28 in (1973) |
| September 4 | 100.0°F (1950) | 28.0°F (1956) | 1.01 in (1965) |
| September 5 | 99.0°F (1998) | 28.0°F (1965) | 1.75 in (1996) |
| September 6 | 100.0°F (1976) | 32.0°F (1956) | 1.15 in (2015) |
| September 7 | 96.1°F (2022) | 30.0°F (1964) | 0.37 in (2019) |
| September 8 | 96.1°F (2003) | 21.0°F (2020) | 0.98 in (2013) |
| September 9 | 96.1°F (1994) | 28.0°F (1962) | 1.05 in (1950) |
| September 10 | 93.9°F (2005) | 25.0°F (1955) | 0.52 in (1963) |
| September 11 | 91.9°F (1948) | 24.1°F (1955) | 1.05 in (1978) |
| September 12 | 96.1°F (1969) | 25.0°F (1987) | 1.68 in (2019) |
| September 13 | 93.9°F (1969) | 21.9°F (1970) | 1.66 in (1954) |
| September 14 | 97.0°F (1946) | 21.9°F (1949) | 0.33 in (2025) |
| September 15 | 96.1°F (1948) | 23.0°F (2007) | 0.50 in (1942) |
| September 16 | 93.9°F (1979) | 24.1°F (1973) | 2.17 in (1963) |
| September 17 | 93.9°F (1976) | 27.0°F (1960) | 0.48 in (2006) |
| September 18 | 93.0°F (1941) | 21.9°F (2010) | 1.23 in (1988) |
| September 19 | 93.0°F (2021) | 17.1°F (1957) | 1.19 in (1978) |
| September 20 | 90.0°F (1938) | 18.0°F (1995) | 1.10 in (2011) |
| September 21 | 93.9°F (1938) | 19.0°F (1995) | 0.82 in (2018) |
| September 22 | 93.9°F (1938) | 19.9°F (1983) | 0.97 in (1959) |
| September 23 | 90.0°F (1992) | 25.0°F (1951) | 0.53 in (2016) |
| September 24 | 90.0°F (1949) | 24.1°F (1947) | 0.57 in (2016) |
| September 25 | 87.1°F (2009) | 19.9°F (1939) | 1.20 in (1959) |
| September 26 | 95.0°F (2014) | 18.0°F (1942) | 0.79 in (1959) |
| September 27 | 90.0°F (2014) | 17.1°F (1942) | 0.70 in (1982) |
| September 28 | 89.1°F (2021) | 19.9°F (1941) | 1.02 in (1982) |
| September 29 | 91.9°F (2021) | 19.9°F (1939) | 0.55 in (1937) |
| September 30 | 91.9°F (2024) | 15.1°F (1961) | 0.62 in (1983) |