September weather in Mequon, WI
The average temperature in Mequon in September is 61.1°F (49.9°F–72.2°F). Average precipitation: 3.22 inches.
September is a fall month in Mequon, and is warmer than the annual average of 45.8°F. Daily temperatures swing about 22.3°F between overnight low and afternoon high. Expect about 10 days with precipitation. Daylight averages about 12h 17m. For travel, September is a comfortable month to visit.
Avg High
72.2°F
Avg Low
49.9°F
Precipitation
3.22 in
Daylight
12h 17m
September records in Mequon
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 99.0°F (1953) | 28.0°F (1993) | 1.35 in (1981) |
| September 2 | 97.0°F (1953) | 34.0°F (1987) | 1.40 in (2002) |
| September 3 | 93.0°F (1953) | 37.9°F (1946) | 2.21 in (2018) |
| September 4 | 93.0°F (2023) | 35.1°F (1974) | 0.92 in (1953) |
| September 5 | 91.0°F (2023) | 27.0°F (1986) | 2.07 in (2008) |
| September 6 | 91.9°F (1954) | 35.1°F (1950) | 1.19 in (2018) |
| September 7 | 93.0°F (1959) | 32.0°F (1993) | 2.00 in (1970) |
| September 8 | 95.0°F (1985) | 34.0°F (1993) | 2.00 in (2001) |
| September 9 | 96.1°F (1955) | 35.1°F (1975) | 2.60 in (1985) |
| September 10 | 91.0°F (1991) | 37.9°F (1995) | 1.33 in (1965) |
| September 11 | 93.0°F (2013) | 37.0°F (1967) | 4.07 in (1986) |
| September 12 | 91.0°F (1948) | 33.1°F (1955) | 1.86 in (1978) |
| September 13 | 91.0°F (1948) | 33.1°F (1964) | 2.25 in (1961) |
| September 14 | 91.0°F (1998) | 34.0°F (1975) | 1.99 in (1961) |
| September 15 | 89.1°F (1948) | 36.0°F (1964) | 0.95 in (1998) |
| September 16 | 91.0°F (1948) | 32.0°F (1984) | 1.02 in (1990) |
| September 17 | 91.0°F (1948) | 34.0°F (1993) | 1.38 in (1992) |
| September 18 | 91.9°F (1955) | 36.0°F (1956) | 2.50 in (1972) |
| September 19 | 90.0°F (1948) | 30.0°F (2012) | 3.20 in (1960) |
| September 20 | 88.0°F (2024) | 28.0°F (1956) | 1.74 in (1965) |
| September 21 | 87.1°F (2024) | 32.0°F (1991) | 2.53 in (1947) |
| September 22 | 88.0°F (2024) | 28.0°F (1976) | 1.51 in (1988) |
| September 23 | 93.0°F (2017) | 24.1°F (1993) | 1.45 in (2024) |
| September 24 | 93.0°F (2017) | 25.0°F (1976) | 1.47 in (1968) |
| September 25 | 91.0°F (2017) | 30.0°F (1985) | 1.24 in (1973) |
| September 26 | 90.0°F (2017) | 28.9°F (1947) | 1.74 in (1951) |
| September 27 | 87.1°F (1998) | 28.0°F (1991) | 1.57 in (1996) |
| September 28 | 87.1°F (1952) | 26.1°F (1964) | 1.28 in (1999) |
| September 29 | 91.9°F (1953) | 27.0°F (1951) | 1.10 in (1986) |
| September 30 | 84.0°F (2025) | 21.9°F (1993) | 0.90 in (1981) |