September weather in St. Helena, CA
The average temperature in St. Helena in September is 70.2°F (53.8°F–86.6°F). Average precipitation: 0.06 inches.
September is a fall month in St. Helena, and is warmer than the annual average of 61°F. Daily temperatures swing about 32.8°F between overnight low and afternoon high. Expect about 1 days with precipitation. Daylight averages about 12h 14m. For travel, September is a comfortable month to visit.
Avg High
86.6°F
Avg Low
53.8°F
Precipitation
0.06 in
Daylight
12h 14m
September records in St. Helena
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 113.0°F (2017) | 39.9°F (1927) | 0.00 in (1908) |
| September 2 | 113.0°F (1955) | 41.0°F (1927) | 0.04 in (1941) |
| September 3 | 111.9°F (1950) | 39.9°F (1921) | 0.02 in (1940) |
| September 4 | 107.1°F (1950) | 37.0°F (1933) | 0.00 in (1908) |
| September 5 | 111.9°F (2022) | 39.0°F (1933) | 2.10 in (1912) |
| September 6 | 113.0°F (2020) | 43.0°F (1921) | 0.75 in (1912) |
| September 7 | 109.9°F (1923) | 39.9°F (1922) | 0.40 in (1985) |
| September 8 | 109.0°F (1944) | 41.0°F (1933) | 0.32 in (1919) |
| September 9 | 111.9°F (1944) | 37.9°F (1931) | 0.86 in (1978) |
| September 10 | 105.1°F (1922) | 39.9°F (1911) | 0.37 in (1978) |
| September 11 | 104.0°F (2015) | 37.9°F (1910) | 0.08 in (1976) |
| September 12 | 107.1°F (1971) | 39.9°F (1915) | 2.48 in (1918) |
| September 13 | 109.9°F (1971) | 35.1°F (1921) | 0.95 in (1918) |
| September 14 | 111.0°F (1971) | 35.1°F (1921) | 0.38 in (1955) |
| September 15 | 106.0°F (1913) | 37.0°F (1921) | 0.41 in (1989) |
| September 16 | 109.0°F (1913) | 37.0°F (1921) | 0.85 in (1982) |
| September 17 | 107.1°F (1913) | 39.9°F (1922) | 0.30 in (1925) |
| September 18 | 106.0°F (1913) | 37.9°F (1908) | 3.66 in (1959) |
| September 19 | 104.0°F (1919) | 33.1°F (1926) | 0.58 in (1977) |
| September 20 | 107.1°F (1919) | 35.1°F (1926) | 0.32 in (1973) |
| September 21 | 108.0°F (1939) | 36.0°F (1926) | 0.40 in (2013) |
| September 22 | 108.0°F (1939) | 37.0°F (1926) | 0.33 in (1923) |
| September 23 | 107.1°F (1939) | 39.0°F (1941) | 0.76 in (1982) |
| September 24 | 106.0°F (1964) | 37.0°F (1928) | 0.32 in (1981) |
| September 25 | 100.9°F (1937) | 35.1°F (1934) | 0.90 in (1923) |
| September 26 | 102.9°F (1921) | 33.1°F (1929) | 0.63 in (1986) |
| September 27 | 108.0°F (1921) | 37.0°F (1934) | 1.15 in (1957) |
| September 28 | 106.0°F (1921) | 35.1°F (1929) | 0.52 in (1976) |
| September 29 | 100.0°F (1966) | 33.1°F (1929) | 0.38 in (1909) |
| September 30 | 100.9°F (1933) | 35.1°F (1926) | 0.26 in (1983) |