Historical weather data, all-time temperature records, and monthly climate averages for Union City, CA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5 in Union City typically brings mild spring conditions, with highs averaging 65° and lows around 46°. There's a modest 24% chance of rain today — not unlikely, but not a sure thing either. The date's range tells an interesting story: as recently as 2016, temperatures hit 80°, while 2012 bottomed out at a chilly 37°.
Union City's weather has some teeth when it wants to. The all-time high of 108° on June 14, 2000 stands as a reminder of how brutal Bay Area heat waves can get, while a record low of 26° on January 13, 2007 proves winter has real bite here too. The wettest single day on record — 3.08 inches on New Year's Eve 2022 — came as a dramatic close to the year.
Union City runs warmest from late August through early September, when average highs peak around 81°, and coolest in late December, when highs dip to 57°. The rainy season and the coldest stretch overlap almost perfectly — the last week of December is both the wettest and coldest of the year, averaging nearly an inch of precipitation. If you're chasing sunshine and warmth, July through September is the sweet spot.