December weather forecast and climate
Hercules, CA

Weather in December

December, the first month of the winter, in Hercules, is still a mild month, with temperature in the range of an average high of 55.4°F (13°C) and an average low of 43.9°F (6.6°C).

Temperature

The coldest month is December, with an average high-temperature of 55.4°F (13°C) and an average low-temperature of 43.9°F (6.6°C).

Humidity

In Hercules, California, the average relative humidity in December is 71%.

Rainfall

In Hercules, during 10.4 rainfall days, 2.13" (54mm) of precipitation is typically accumulated. In Hercules, during the entire year, the rain falls for 72.2 days and collects up to 12.83" (326mm) of precipitation.

Ocean temperature

In Hercules, the average water temperature is 54.1°F (12.3°C).
Note: Swimming in 54.1°F (12.3°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

Daylight

With an average of 9.6h of daylight, December has the shortest days of the year in Hercules.

Sunshine

With an average of 5.7h of sunshine, December has the least sunshine of the year in Hercules.

UV index

January, February, November and December, with an average maximum UV index of 3, are months with the lowest UV index in Hercules, California. A UV Index value of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV rays for average individuals.
Note: The average daily UV index of 3 in December transform into the following instructions:
Take precautions. Light skin individuals may get burned in less than 30 minutes. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.
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FAQ

What is the coldest month in Hercules?

The coldest month in Hercules, California, is December, with an average high-temperature of 55.4°F (13°C) and an average low-temperature of 43.9°F (6.6°C).

What is the temperature in December in Hercules?

The average high-temperature, in December, in Hercules, is 55.4°F (13°C), while the average low-temperature is 43.9°F (6.6°C).

What is the average humidity in December in Hercules?

In Hercules, the average relative humidity in December is 71%.

How many days does it rain in December in Hercules?

In December, in Hercules, California, the rain falls for 10.4 days. Throughout December, 2.13" (54mm) of precipitation is accumulated.

How cold is the water in December in Hercules?

In Hercules, in December, the average water temperature is 54.1°F (12.3°C). At temperatures below 50°F (10°C), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 55.4°F (13°C) is not comfortable.

What is the month with the shortest days in Hercules?

With an average of 9.6h of daylight, December has the shortest days of the year in Hercules, California.

How many hours of daylight does Hercules have in December?

The average length of the day in December in Hercules, California, is 9.6h.

What is the month with the least sunshine in Hercules?

December has the least sunshine of the year in Hercules, with an average of 5.7h of sunshine.

How many hours of sunshine does Hercules have in December?

In Hercules, the average sunshine in December is 5.7h.

What is the month with the lowest UV index in Hercules?

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

What is the UV index intensity in December in Hercules?

The average daily maximum UV index in December in Hercules, California, is 3. A UV Index reading of 3 to 5 represents a medium health risk from the exposure to the Sun's UV radiation.

Average temperature in December
Hercules, CA

Average temperature in December - Hercules, CA
  • Average high temperature in December: 55.4°F

The warmest month (with the highest average high temperature) is September (77.5°F).
The month with the lowest average high temperature is December (55.4°F).

  • Average low temperature in December: 43.9°F

The month with the highest average low temperature is August (56.8°F).
The coldest months (with the lowest average low temperature) are January and December (43.9°F).

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Average pressure in December
Hercules, CA

Average pressure in December - Hercules, CA
  • Average pressure in December: 30.11"

The month with the highest atmospheric pressure is January (30.13").
Months with the lowest atmospheric pressure are June, August and September (29.92").

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Average wind speed in December
Hercules, CA

Average wind speed in December - Hercules, CA
  • Average wind speed in December: 5.5mph

The windiest month (with the highest average wind speed) is May (7.5mph).
The calmest month (with the lowest average wind speed) is November (4.8mph).

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Average humidity in December
Hercules, CA

Average humidity in December - Hercules, CA
  • Average humidity in December: 71%

The month with the highest relative humidity is March (74%).
Months with the lowest relative humidity are September and October (63%).

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Average rainfall in December
Hercules, CA

Average rainfall in December - Hercules, CA
  • Average rainfall in December: 2.13"

The wettest month (with the highest rainfall) is February (2.76").
The driest months (with the least rainfall) are July and August (0.04").

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Average rainfall days in December
Hercules, CA

Average rainfall days in December - Hercules, CA
  • Average rainfall days in December: 10.4 days

The month with the highest number of rainy days is March (12.6 days).
The month with the least rainy days is August (1.1 days).

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Average sea temperature in December
Hercules, CA

Average sea temperature in December - Hercules, CA
  • Average sea temperature in December: 54.2°F

The best month for swimming (with the highest average sea temperature) is September (57°F).
The coldest month (with the lowest average sea temperature) is April (52.6°F).

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Average daylight in December /
Average sunshine in December
Hercules, CA

Average daylight in December / Average sunshine in December - Hercules, CA
  • Average daylight in December: 9.6h

The month with the longest days is June (Average daylight: 14.8h).
The month with the shortest days is December (Average daylight: 9.6h).

  • Average sunshine in December: 5.7h

The month with the most sunshine is July (Average sunshine: 11.9h).
The month with the least sunshine is December (Average sunshine: 5.7h).

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Average sunshine days in December
Hercules, CA

Average sunshine days in December - Hercules, CA
  • Average sunshine days in December: 19.5 days

The month with the most sunshine days is August (27.3 days).
The month with the least sunshine days is March (16.4 days).

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Average UV index in December
Hercules, CA

Average UV index in December - Hercules, CA
  • Average UV index in December: 3

Months with the highest UV index are April, May, June, July, August and September (UV index 5).
Months with the lowest UV index are January, February, November and December (UV index 3).

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Average cloud cover in December
Hercules, CA

Average cloud cover in December - Hercules, CA
  • Average cloud cover in December: 36

The month with the most cloud cover is March (Cloud cover 37).
The month with the least cloud cover is July (Cloud cover 12).

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Average visibility in December
Hercules, CA

Average visibility in December - Hercules, CA
  • Average visibility in December: 6mi

Months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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