Union City, CA Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Union City, a city in Alameda County, California.
Tonight
58°F
Mostly Cloudy
Mostly cloudy, with a low around 58. West wind 2 to 6 mph.
7-day forecast for Union City
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 58°F | Mostly Cloudy | 2 to 6 mph W | 0% |
| Saturday | 79°F | Mostly Sunny | 2 to 9 mph W | 0% |
| Saturday Night | 58°F | Mostly Cloudy | 3 to 8 mph W | 0% |
| Sunday | 72°F | Mostly Cloudy | 3 to 9 mph WSW | 3% |
| Sunday Night | 58°F | Mostly Cloudy | 3 to 9 mph WSW | 3% |
| Monday | 75°F | Partly Sunny | 3 to 10 mph WSW | 0% |
| Monday Night | 57°F | Partly Cloudy | 2 to 10 mph WSW | 0% |
| Tuesday | 77°F | Sunny | 2 to 9 mph WSW | 0% |
| Tuesday Night | 57°F | Mostly Clear | 1 to 9 mph WSW | 0% |
| Wednesday | 86°F | Sunny | 1 to 9 mph SW | 0% |
| Wednesday Night | 62°F | Mostly Clear | 1 to 9 mph W | 0% |
| Thursday | 87°F | Sunny | 0 to 9 mph WSW | 0% |
| Thursday Night | 62°F | Partly Cloudy | 2 to 9 mph WSW | 0% |
| Friday | 81°F | Mostly Sunny | 2 to 10 mph W | 0% |
Forecast source: National Weather Service (api.weather.gov) for Union City (37.603, -122.019). Updated through the day.
Growing snapshot for Union City
Last spring frost
Jan 2
First fall frost
Dec 25
Growing season
365 days
Hardiness zone
9b
More local growing data for Union City: nearby ZIP 94544 weather · frost dates · planting calendar · California frost dates
Nearby towns & communities
Alameda
Albany
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Berkeley
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Cherryland
Dublin
Emeryville
Fairview
Fremont
Hayward
Kensington
Livermore
Mountain House
Newark
Oakland
Piedmont
Pleasanton
San Leandro
San Lorenzo
Sunol
Climate data from the nearest NOAA station, Hayward Air Terminal, Ca (3.5 mi from Union City). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.