Union City, California Weather
Summer heat deepens across the valleys. Day 15 of summer. Read this microseason across nine climate regions →
Union City weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 5Overcast——71°56°—
- MondayJul 6Overcast——68°54°-3°
- TuesdayJul 7Overcast——76°55°+8°
- WednesdayJul 8Clear——81°55°+5°
- ThursdayJul 9Clear——83°59°+2°
- FridayJul 10Overcast——85°58°+2°
- SaturdayJul 11Overcast——88°63°+3°
AQI 36 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 8.4 µg/m³ (AQI 47) with a 0.71 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 30 now. With UV 7.9 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 31 around 1 PM.
- Present
- AQI 30
- UV peak
- 7.9 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 31
PM × Wind × Precip
PM2.5 at 8.4 µg/m³ (AQI 47) with a 0.71 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.71
- Wind
- calm
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
- Moonrise
- 11:27 PM
- Moonset
- 11:27 AM
- In sign
- ♓︎ Pisces
Summer heat deepens across the valleys
Union City at a glance
- Today vs. normal: 13°F below the seasonal normal for this latitude
- Last frost: April 2 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
ZIP code: 94587
16-Day Forecast — Union City
- Sun71°56°1%
- Mon68°54°1%
- Tue76°55°0%
- Wed81°55°0%
- Thu83°59°0%
- Fri85°58°0%
- Sat88°63°1%
- Sun81°64°1%
- Mon91°66°3%
- Tue91°64°5%
- Wed89°64°1%
- Thu90°62°3%
- Fri94°66°0%
- Sat86°64°0%
- Sun84°62°3%
- Mon84°60°3%
Forecast data from Open-Meteo (CC BY 4.0).
Live wind & temperature near Union City
Right now in the garden
Peak growing season
As of July 5, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
Microseason · July 1–5
Summer heat deepens across the valleys
Inland temperatures exceed 95°F regularly; fire danger reaches moderate to high across most of the region.
Day 186 of 365 · Wedge 37 of 72
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | lettuce, peas, spinach, radishes | — |
| May | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | — | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | fall brassicas, garlic (overwinter), carrots | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
Union City peaks at about 68°F in August and bottoms near 51°F in December; February brings the heaviest rain (3.2 inches) and July the least (0.0 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 51° | 3.0″ | 6 |
| February | 53° | 3.2″ | 7 |
| March | 56° | 2.5″ | 6 |
| April | 58° | 1.2″ | 4 |
| May | 62° | 0.5″ | 2 |
| June | 65° | 0.2″ | 0 |
| July | 67° | 0.0″ | 0 |
| August | 68° | 0.0″ | 0 |
| September | 67° | 0.1″ | 0 |
| October | 63° | 0.7″ | 2 |
| November | 55° | 1.6″ | 4 |
| December | 51° | 3.0″ | 7 |
Regional context
In Union City, NOAA NCEI 1991-2020 normals put January near 51°F and July near 67°F — a 17°F seasonal arc — with about 15.9 inches of precipitation over 37 rainy or snowy days.
Union City's moisture rides winter storm tracks: February brings 3.2 inches over 6.8 wet days, while July sees only 0.0 inches across 0.0 days in the dry warm season. It is a winter-storm rhythm Union City shares with places like Hayward, CA, Fairview, CA and Fremont, CA.
With a coldest-month mean of 51°F, Union City stays mostly frost-free and grows year-round. The August peak near 68°F is Union City's real limit, pushing cool-season vegetables to spring and fall. Across Union City, elevation and tree cover drive a 4-7°F spread in Union City's overnight lows.
Similar climates: Hayward, CA, Fairview, CA, Fremont, CA, Newark, CA, Cherryland, CA.
Frequently asked
- When does it freeze in Union City?
- Union City's last spring frost lands near mid-April, and in Union City the first fall frost follows around mid-November.
- What is the rainy season in Union City?
- Rainfall in Union City peaks in February near 3.2 inches, out of about 16 inches annually.
- What is the warmest month in Union City?
- The warmest stretch in Union City comes in August, around 68°F on average.
- What is the coldest month in Union City?
- On average December is the chilliest month in Union City, about 51°F.
- When can I start a vegetable garden in Union City?
- Frost-hardy sowings begin at mid-April in Union City; warm-season starts follow two weeks on.
- How many rainy days does Union City get?
- Expect roughly 37 wet days a year in Union City.
- What hardiness zone is Union City?
- Union City sits in the USDA zone set by December lows near 51°F; the USDA ZIP tool gives the band.
- What is the 10-day forecast for Union City?
- Union City's extended outlook — daily high and low temperatures and precipitation chances for each upcoming day — is in the daily forecast above.
- Will it rain this week in Union City?
- See this week's day-by-day rain chances for Union City in the daily forecast above, and the next 24 hours in the hourly chart.
- What is the weather like right now in Union City?
- Current conditions for Union City and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
- How often is the Union City forecast updated?
- The Union City forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
- When are sunrise and sunset in Union City?
- Today's sunrise and sunset times for Union City are in the Almanac section above, along with civil dawn, civil dusk, and day length. Day length is longest near the summer solstice and shortest near the winter solstice.
- How accurate is the weather forecast for Union City?
- The next few days in Union City's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.
Climate
Union City's hot-summer Mediterranean climate in California pairs 51°F Januarys with 67°F Julys, 16°F apart across the seasons.
Yearly precipitation in Union City totals around 16 inches, spread over about 37 days of rain or snow.
The 16°F gap between Union City's summer and winter, at 37.6°N, shapes Union City's frost calendar.
ZIP codes in Union City
- 94552
- 94587