September weather in Boise City, ID
The average temperature in Boise City in September is 66.3°F (52.6°F–80.0°F). Average precipitation: 0.43 inches.
September is a fall month in Boise City, and is warmer than the annual average of 53.2°F. Daily temperatures swing about 27.4°F between overnight low and afternoon high. Expect about 4 days with precipitation. Daylight averages about 12h 17m. For travel, September is one of the best months of the year to visit.
Avg High
80.0°F
Avg Low
52.6°F
Precipitation
0.43 in
Daylight
12h 17m
September records in Boise City
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 102.0°F (1945) | 41.0°F (1977) | 0.65 in (1964) |
| September 2 | 100.9°F (1950) | 42.1°F (1999) | 0.15 in (2000) |
| September 3 | 102.0°F (2022) | 37.0°F (1956) | 0.49 in (2013) |
| September 4 | 102.0°F (2020) | 39.9°F (1969) | 0.23 in (1940) |
| September 5 | 100.0°F (1963) | 36.0°F (1969) | 0.46 in (1972) |
| September 6 | 100.9°F (2022) | 39.9°F (1945) | 0.43 in (1978) |
| September 7 | 104.0°F (2022) | 34.0°F (1976) | 0.32 in (1947) |
| September 8 | 98.1°F (2024) | 37.0°F (1946) | 0.71 in (1986) |
| September 9 | 98.1°F (2021) | 34.0°F (1970) | 0.75 in (1950) |
| September 10 | 97.0°F (1990) | 36.0°F (1989) | 0.48 in (1980) |
| September 11 | 97.0°F (1963) | 35.1°F (1982) | 1.73 in (1976) |
| September 12 | 93.9°F (1963) | 32.0°F (1970) | 0.26 in (1980) |
| September 13 | 93.9°F (1945) | 30.9°F (1970) | 0.34 in (2001) |
| September 14 | 100.9°F (2000) | 23.0°F (1970) | 0.61 in (1959) |
| September 15 | 93.9°F (1995) | 36.0°F (1970) | 0.42 in (1996) |
| September 16 | 93.0°F (1943) | 33.1°F (1965) | 0.20 in (1977) |
| September 17 | 95.0°F (1981) | 24.1°F (1965) | 0.65 in (1989) |
| September 18 | 96.1°F (1981) | 27.0°F (1965) | 0.41 in (1959) |
| September 19 | 93.9°F (2008) | 30.9°F (1978) | 0.66 in (1959) |
| September 20 | 89.1°F (1966) | 33.1°F (1983) | 0.90 in (2008) |
| September 21 | 95.0°F (1967) | 30.0°F (1993) | 0.15 in (2016) |
| September 22 | 99.0°F (1966) | 30.9°F (1955) | 0.07 in (1945) |
| September 23 | 93.9°F (1987) | 28.9°F (1984) | 0.35 in (2007) |
| September 24 | 98.1°F (2011) | 28.0°F (1984) | 0.64 in (1986) |
| September 25 | 95.0°F (1963) | 28.0°F (1972) | 0.51 in (1998) |
| September 26 | 93.0°F (1963) | 35.1°F (1961) | 0.50 in (1990) |
| September 27 | 95.0°F (2022) | 32.0°F (1945) | 0.39 in (1986) |
| September 28 | 95.0°F (1963) | 30.9°F (1999) | 0.34 in (2014) |
| September 29 | 95.0°F (1992) | 27.0°F (1954) | 0.66 in (2025) |
| September 30 | 96.1°F (1992) | 28.9°F (1954) | 0.61 in (1983) |