Union City (CA) Weather & Climate: Best Time to Visit
Average temperatures, rainfall, sunshine and the best time to visit Union City.
Climate overview of Union City
Temperatures in Union City, California, United States of America, shift moderately through the seasons. The warmest month is September at 25°C (77°F), and the coolest is December at 15°C (59°F).
The city tends toward dry conditions, with around 354 mm (14 in) of rainfall per year. It does, however, have a distinct dry season from April to November, with warm summers and mild winters. May is the sunniest month, averaging 10.8 hours of sunshine per day.
Union City Weather by Month
Pick a month to see the average temperature, rainfall and sunshine in Union City - and find the best time to visit.
Monthly Temperature in Union City
The climate in Union City experiences moderate temperature changes, with mild shifts between seasons. Typically, average maximum daytime temperatures range from a comfortable 25°C (77°F) in September to a moderate 15°C (59°F) in the coolest month, December.
Nights vary from 14°C (57°F) in September to around 6°C (43°F) during the colder months.
Check out our detailed temperature page for more information.
Temperature ranges by month
Rainfall in Union City
Union City has a relatively dry climate with low precipitation, averaging 354 mm (14 in) of rainfall annually. The climate in Union City shows significant variation throughout the year. Expect moderate rainfall in December, the wettest month, with an average of 81 mm (3.2 in) of precipitation over 11 rainy days.
In contrast, the driest month July offers drier and sunnier days, with around 0 mm (0 in) of rainfall over 0 rainy days. For more details, please visit our Union City Precipitation page.
The mean monthly precipitation over the year, including rain, hail, and snow
The average number of days each month with precipitation
Sunshine Hours in Union City
For those who appreciate different seasons, Union City serves as an ideal destination. Expect longer, more sun-filled days in May with an average of 10.8 hours of sunshine daily, and embrace the darker days in December, offering only 5.3 hours of daily sunlight.
Visit our detailed sunshine hours page for more information.
Monthly hours of sunshine
Daily hours of sunshine
Daily percentage of sunshine
Humidity in Union City by Month
The relative humidity is high throughout the year in Union City.
The city experiences its highest humidity in January, reaching 80%. In June, the humidity drops to its lowest level at 71%. What does this mean? Read our detailed page on humidity levels for further details.
Relative humidity over the year
Best Time to Visit Union City
Monthly ratings reflect general weather comfort, based on daytime temperature and rainfall. Swimming and winter conditions are highlighted separately where relevant.
- Best overall: April, May, June, July, August, September and October
- Warmest weather: July, August and September
- Most sunshine: April, May, June and July
- Fewest rainy days: June, July, August and September
- Seasonal pattern: A distinct dry season from April to November, with warm summers and mild winters
Frequently asked questions about the climate in Union City
What is the best time to visit Union City?
April, May, June, July, August, September and October typically offer the most optimal weather in Union City. In contrast, January, February and December tend to have less optimal conditions. Union City has a distinct dry season from April to November, with warm summers and mild winters.
What temperatures can I expect in Union City?
Daytime highs range from 15°C (59°F) in December to 25°C (77°F) in September. Nighttime lows range from 6°C (43°F) to 14°C (57°F).
How much rain does Union City get?
Annual rainfall is around 354 mm (14 in). December is the wettest month with 81 mm (3.2 in), while July is the driest with 0 mm (0 in).
How sunny is Union City?
Union City receives around 3,058 hours of sunshine per year. May is the sunniest month with 324 hours, while December is the cloudiest with just 160 hours. Overall, Union City enjoys abundant sunshine.
Union City 3-Day Forecast
Union City (CA) 3-Day Forecast
Union City on the map
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