September weather in Union City, CA
The average temperature in Union City in September is 67.2°F (56.0°F–78.3°F). Average precipitation: 0.10 inches.
September is a fall month in Union City, and is warmer than the annual average of 59.5°F. Daily temperatures swing about 22.3°F between overnight low and afternoon high. Expect about 1 days with precipitation. Daylight averages about 12h 14m. For travel, September is one of the best months of the year to visit.
Avg High
78.3°F
Avg Low
56.0°F
Precipitation
0.10 in
Daylight
12h 14m
September records in Union City
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 100.9°F (2017) | 51.1°F (1999) | 0.08 in (2000) |
| September 2 | 104.0°F (2017) | 51.1°F (2012) | 0.01 in (2000) |
| September 3 | 100.9°F (2017) | 51.1°F (1999) | 0.02 in (2003) |
| September 4 | 95.0°F (2008) | 50.0°F (2021) | 0.00 in (1996) |
| September 5 | 97.0°F (2022) | 51.1°F (2000) | 0.00 in (1996) |
| September 6 | 102.0°F (2022) | 48.9°F (1996) | 0.00 in (1996) |
| September 7 | 99.0°F (2020) | 48.9°F (1999) | 0.00 in (1996) |
| September 8 | 98.1°F (2022) | 50.0°F (2002) | 0.00 in (1996) |
| September 9 | 95.0°F (2015) | 51.1°F (1999) | 0.05 in (1999) |
| September 10 | 93.9°F (2015) | 50.0°F (2012) | 0.00 in (1996) |
| September 11 | 91.0°F (2003) | 48.9°F (1999) | 0.00 in (1996) |
| September 12 | 95.0°F (2003) | 51.1°F (1996) | 0.15 in (2017) |
| September 13 | 97.0°F (2003) | 51.1°F (1999) | 0.00 in (1996) |
| September 14 | 93.9°F (2019) | 51.1°F (2018) | 0.33 in (2009) |
| September 15 | 90.0°F (2004) | 51.1°F (2021) | 0.00 in (1996) |
| September 16 | 86.0°F (2025) | 50.0°F (1996) | 0.21 in (2019) |
| September 17 | 93.0°F (2000) | 50.0°F (2006) | 0.00 in (1996) |
| September 18 | 98.1°F (2000) | 50.0°F (2005) | 0.06 in (2022) |
| September 19 | 97.0°F (2000) | 48.9°F (2008) | 0.41 in (2022) |
| September 20 | 93.9°F (2015) | 46.9°F (2004) | 0.15 in (2005) |
| September 21 | 96.1°F (2015) | 46.9°F (2004) | 0.62 in (2013) |
| September 22 | 93.9°F (2003) | 48.9°F (2004) | 0.18 in (2007) |
| September 23 | 93.9°F (1997) | 48.0°F (2017) | 0.00 in (1996) |
| September 24 | 96.1°F (1997) | 46.9°F (1999) | 0.01 in (2025) |
| September 25 | 93.9°F (2019) | 48.0°F (1999) | 0.40 in (2014) |
| September 26 | 95.0°F (1999) | 46.9°F (2013) | 0.01 in (2023) |
| September 27 | 95.0°F (1999) | 46.9°F (2013) | 0.01 in (2021) |
| September 28 | 96.1°F (2010) | 50.0°F (2013) | 0.00 in (1996) |
| September 29 | 93.0°F (1997) | 46.0°F (2007) | 0.00 in (1996) |
| September 30 | 93.0°F (2001) | 46.9°F (2009) | 0.04 in (2015) |