September weather in Roundup, MT
The average temperature in Roundup in September is 59.6°F (42.4°F–76.9°F). Average precipitation: 1.20 inches.
September is a fall month in Roundup, and is warmer than the annual average of 46.5°F. Daily temperatures swing about 34.5°F between overnight low and afternoon high. Expect about 5 days with precipitation. Daylight averages about 12h 19m. For travel, September is a comfortable month to visit.
Avg High
76.9°F
Avg Low
42.4°F
Precipitation
1.20 in
Daylight
12h 19m
September records in Roundup
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 102.0°F (1983) | 34.0°F (1930) | 0.95 in (1973) |
| September 2 | 99.0°F (1940) | 32.0°F (1959) | 0.38 in (1935) |
| September 3 | 100.0°F (1950) | 30.0°F (1961) | 0.74 in (1984) |
| September 4 | 102.0°F (1950) | 28.0°F (1962) | 0.66 in (1936) |
| September 5 | 99.0°F (1998) | 33.1°F (1956) | 1.24 in (2010) |
| September 6 | 97.0°F (1976) | 32.0°F (1956) | 0.45 in (2001) |
| September 7 | 98.1°F (1944) | 33.1°F (1972) | 0.33 in (1976) |
| September 8 | 97.0°F (1979) | 30.0°F (1943) | 0.82 in (1970) |
| September 9 | 99.0°F (1942) | 24.1°F (1962) | 0.90 in (2013) |
| September 10 | 98.1°F (2017) | 30.0°F (1992) | 1.18 in (1961) |
| September 11 | 96.1°F (1959) | 21.9°F (1921) | 0.77 in (2008) |
| September 12 | 96.1°F (2017) | 26.1°F (1989) | 1.91 in (1978) |
| September 13 | 95.0°F (2017) | 26.1°F (1989) | 0.81 in (1954) |
| September 14 | 99.0°F (1948) | 26.1°F (1989) | 0.85 in (1934) |
| September 15 | 96.1°F (2000) | 26.1°F (1989) | 0.93 in (2017) |
| September 16 | 95.0°F (2000) | 26.1°F (1936) | 0.96 in (2017) |
| September 17 | 98.1°F (1943) | 21.9°F (1965) | 0.50 in (1996) |
| September 18 | 95.0°F (1937) | 24.1°F (2003) | 1.27 in (1978) |
| September 19 | 96.1°F (1981) | 26.1°F (1943) | 1.15 in (1983) |
| September 20 | 95.0°F (1938) | 25.0°F (1983) | 1.00 in (1914) |
| September 21 | 95.0°F (1938) | 21.9°F (1972) | 0.90 in (1991) |
| September 22 | 93.9°F (1938) | 21.0°F (1961) | 0.85 in (2017) |
| September 23 | 93.0°F (1966) | 25.0°F (1931) | 0.50 in (1937) |
| September 24 | 93.0°F (1938) | 21.9°F (1934) | 0.60 in (1931) |
| September 25 | 98.1°F (2015) | 21.9°F (1984) | 0.90 in (1986) |
| September 26 | 96.1°F (2015) | 19.0°F (1972) | 0.35 in (2013) |
| September 27 | 91.9°F (2015) | 21.0°F (1961) | 0.67 in (1947) |
| September 28 | 91.9°F (1967) | 21.9°F (1972) | 0.40 in (1919) |
| September 29 | 91.9°F (1967) | 21.0°F (1972) | 0.55 in (1981) |
| September 30 | 91.0°F (1963) | 15.1°F (1985) | 0.55 in (2018) |