December weather forecastUnion City, CA
December
Weather in December
December, the first month of the winter in Union City, is also a moderate month, with an average temperature fluctuating between 43.7°F (6.5°C) and 56.3°F (13.5°C).Temperature
Union City's temperature records reveal December as the coldest month, marked by average highs of 56.3°F (13.5°C) and lows of 43.7°F (6.5°C).Humidity
The average relative humidity in December is 70%.Rainfall
In Union City, in December, during 6.3 rainfall days, 0.35" (9mm) of precipitation is typically accumulated. In Union City, during the entire year, the rain falls for 38 days and collects up to 2.13" (54mm) of precipitation.Daylight
With an average of 9h and 36min of daylight, December has the shortest days of the year.On the first day of December, sunrise is at 7:05 am and sunset at 4:50 pm. On the last day of the month, sunrise is at 7:22 am and sunset at 5:00 pm PST.
Sunshine
December has the least sunshine of the year, with an average of 6h of sunshine.UV index
The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 3. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for ordinary individuals.Note: The daily maximum UV index of 3 in December interprets into the following advice:
Guard yourself - Avoiding sunburn is suggested. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Select sunglasses that boast both UVA and UVB protection to limit the adverse effects of the sun on the eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Union City, CA
- Average high temperature in December: 56.3°F
The warmest months (with the highest average high temperature) are July and August (80.1°F).
The month with the lowest average high temperature is December (56.3°F).
- Average low temperature in December: 43.7°F
The months with the highest average low temperature are August and September (56.7°F).
The coldest month (with the lowest average low temperature) is December (43.7°F).
Average pressure in December
Union City, CA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in December
Union City, CA
- Average wind speed in December: 5.3mph
The windiest month (with the highest average wind speed) is May (6.4mph).
The calmest months (with the lowest average wind speed) are October and November (4.7mph).
Average humidity in December
Union City, CA
- Average humidity in December: 70%
The month with the highest relative humidity is March (73%).
The months with the lowest relative humidity are September and October (62%).
Average rainfall in December
Union City, CA
- Average rainfall in December: 0.35"
The wettest month (with the highest rainfall) is February (0.47").
The driest months (with the least rainfall) are June, July and August (0").
Average rainfall days in December
Union City, CA
- Average rainfall days in December: 6.3 days
The month with the highest number of rainy days is March (7.3 days).
The month with the least rainy days is July (0.3 days).
Average daylight in December /
Average sunshine in December
Union City, CA
- Average daylight in December: 9h and 36min
The month with the longest days is June (Average daylight: 14h and 42min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in December: 6h and 0min
The month with the most sunshine is July (Average sunshine: 12h and 12min).
The month with the least sunshine is December (Average sunshine: 6h and 0min).
Average sunshine days in December
Union City, CA
- Average sunshine days in December: 24 days
The months with the most sunshine days are July and August (30.4 days).
The month with the least sunshine days is February (22.2 days).
Average UV index in December
Union City, CA
- Average UV index in December: 3
The months with the highest UV index are June and July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in December
Union City, CA
- Average cloud cover in December: 33
The month with the most cloud cover is March (Cloud cover 34).
The month with the least cloud cover is July (Cloud cover 6).
Average visibility in December
Union City, CA
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
