December weather forecast
Union City, CA

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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.
Updated: Aug 26, 2024
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What time of the year is the coldest?

December is the coldest month, with the temperature often reaching an average high of 56.3°F (13.5°C) and an average low of 43.7°F (6.5°C).

What are December temperatures?

In December, in Union City, the average high-temperature is 56.3°F (13.5°C), and the average low-temperature is 43.7°F (6.5°C).

What is the average humidity in December?

The average relative humidity in December is 70%.

How much does it rain in December?

In Union City, in December, it is raining for 6.3 days, with typically 0.35" (9mm) of accumulated precipitation.

What is the month with the shortest days?

December has the shortest days of the year, with an average of 9h and 36min of daylight.

How many hours of daylight does Union City have in December?

In December, the average day length is 9h and 37min.

When is the sunrise / sunset in December?

On the first day of December in Union City, 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.

What is the month with the least sunshine?

The month with the least sunshine in Union City is December, with an average of 6h of sunshine.

How long on average sun shines in December?

The average sunshine duration in December is 6h.

What is the month with the lowest UV index?

January, February, November and December, with an average maximum UV index of 3, are months with the lowest UV index.

How high is the UV index in December?

The average daily maximum UV index in December is 3. A UV Index value of 3 to 5 symbolizes a medium health risk from exposure to Sun's UV rays.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in December
Union City, CA

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 - 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 - 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 - 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 - 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 - 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 / Average sunshine in December - Union City, CA
  • Average daylight in December: 9h and 4min

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 - 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 - 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 - 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 - 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).

Union City, California, USA

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