Hurricanes and Tornadoes That Hit Union City, CA

The nearest NOAA station with 1991–2020 climate normals is Fremont, CA, 4 miles southeast of Union City at 38 feet. August is the warmest, with an average high of 78°F and low of 57°F; December is the coolest, at 58°F and 43°F. February is the wettest at 3.2 inches of precipitation on average and July and August the driest at 0.0 inches; the year adds up to 16.0 inches over 37 days with at least a tenth of an inch. Highs reach 90°F on about 12 days a year, almost all from June to September. Lows fall below freezing on about 3 nights a year. That 16.0 inches is more than at 111 of the 226 California stations used on this site (49%). Hayward, 4 miles northwest, has its own station (Hayward Air Terminal, CA): 16.1 inches a year, 0.1 more than here, and an August average high of 76°F against 78°F.

Water temperature at the NOAA tide station Redwood City, CA, 11 miles southwest, averaged 74°F in August and 54°F in January over 2021–2025. No month averaged 80°F. Sea level at the Redwood City tide gauge, 11 miles from Union City, has risen 1.08 ± 0.25 inches per decade from 1974 to 2025, NOAA's linear trend; at that pace it is 10.8 inches in a hundred years. That is faster than at 62 of the 144 U.S. gauges with a NOAA trend.

Since 1996, the National Weather Service has logged 47 flood, rain, thunderstorm wind and lightning events that began within 10 miles of Union City: 38 floods, 5 flash floods, 2 heavy rain events and 2 thunderstorm wind reports. None is recorded as killing or injuring anyone; the NWS estimated $61,000 in property and crop damage. The strongest thunderstorm gust on record here was 69 mph, on October 19, 2004. February has had the most flash floods, 4 of 5. Of the 550 California cities on this site with a flash flood on record, 163 have had fewer than Union City.

Flood insurance policyholders in Union City's ZIP code 94587 have filed 25 claims with the National Flood Insurance Program since 1986, and were paid $499,000 for buildings and contents, in the dollars of each year. The most came from Pineapple Express - Southern in 1998: 12 claims (48% of all) and $202,000, then Flooding in 1995 with 10. 88% of the claims carry the name of a storm or flood event; the rest have no event name. Of the 415 California cities on this site with 10 or more claims, 125 have fewer than Union City.