December weather forecastHercules, CA
December
Weather in December
The first month of the winter, December, is still a refreshing month in Hercules, California, with an average temperature fluctuating between 55.4°F (13°C) and 43.9°F (6.6°C).Temperature
December, characterized by an average high temperature of 55.4°F (13°C) and a low temperature of 43.9°F (6.6°C), is generally the coldest month.Humidity
In December, the average relative humidity is 71%.Rainfall
In December, the rain falls for 10.4 days. Throughout December, 2.13" (54mm) of precipitation is accumulated. Throughout the year, there are 72.2 rainfall days, and 12.83" (326mm) of precipitation is accumulated.Ocean temperature
In Hercules, in December, the average water temperature is 54.1°F (12.3°C).Note: Swimming in 54.1°F (12.3°C) can be lethal. Merely spending a few minutes in 55.4°F (13°C) waters feels harsh, and venturing below 50°F (10°C) might disrupt breathing control and bring about cold shock, contingent on individual resilience.
Daylight
With an average of 9h and 36min of daylight, December has the shortest days of the year in Hercules, California.On the first day of December in Hercules, sunrise is at 7:07 am and sunset at 4:49 pm. On the last day of the month, sunrise is at 7:25 am and sunset at 4:59 pm PST.
Sunshine
The month with the least sunshine in Hercules is December, with an average of 5.7h of sunshine.UV index
January, February, November and December, with an average maximum UV index of 3, are months with the lowest UV index in Hercules. A UV Index reading of 3 to 5 represents a moderate health risk from unprotected exposure to Sun's UV rays for ordinary individuals.Note: The maximum UV index of 3 during December leads to these instructions:
Act with care - The need to guard against sun damage is communicated. When the Sun's UV radiation is most intense during midday, it's best to find shade and limit exposure. To mitigate harm from sun exposure, pick sunglasses offering UVA and UVB defense.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
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).
Average pressure in December
Hercules, 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
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).
Average humidity in December
Hercules, CA
- Average humidity in December: 71%
The month with the highest relative humidity is March (74%).
The months with the lowest relative humidity are September and October (63%).
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").
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).
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).
Average daylight in December /
Average sunshine in December
Hercules, CA
- Average daylight in December: 9h and 36min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in December: 5h and 42min
The month with the most sunshine is July (Average sunshine: 11h and 54min).
The month with the least sunshine is December (Average sunshine: 5h and 42min).
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).
Average UV index in December
Hercules, CA
- Average UV index in December: 3
The months with the highest UV index are April, May, June, July, August and September (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 3).
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).
Average visibility in December
Hercules, 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).
