December weather forecastSaint Helena, CA
December
Weather in December
December, the first month of the winter in Saint Helena, is also a fresh month, with an average temperature ranging between min 39.6°F (4.2°C) and max 54.5°F (12.5°C).Temperature
With its high average temperature of 54.5°F (12.5°C) and a low of 39.6°F (4.2°C), December is regarded as the coldest month.Humidity
In Saint Helena, the average relative humidity in December is 73%.Rainfall
In December, the rain falls for 11.3 days. Throughout December, 2.95" (75mm) of precipitation is accumulated. In Saint Helena, during the entire year, the rain falls for 76.2 days and collects up to 16.93" (430mm) of precipitation.Snowfall
In Saint Helena, snow does not fall in January, February, April through December.Daylight
With an average of 9h and 30min of daylight, December has the shortest days of the year.On the first day of the month, sunrise is at 7:09 am and sunset at 4:49 pm. On the last day of December, sunrise is at 7:27 am and sunset at 4:59 pm PST.
Sunshine
With an average of 5.3h of sunshine, December has the least sunshine of the year.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 unprotected exposure to Sun's UV rays for the ordinary person.Note: The maximum daily UV index of 3 during December translates into the following directions:
Ensure safety - Recommendations to avert sunburn are presented. For skin protection, it's recommended to minimize Sun exposure during its peak hours around midday. Consider a wide-brim hat essential for effective sun defense covering your face, neck, and eyes.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Saint Helena, CA
- Average high temperature in December: 54.5°F
The warmest month (with the highest average high temperature) is July (88.3°F).
The month with the lowest average high temperature is December (54.5°F).
- Average low temperature in December: 39.6°F
The month with the highest average low temperature is September (54.3°F).
The coldest month (with the lowest average low temperature) is December (39.6°F).
Average pressure in December
Saint Helena, CA
- Average pressure in December: 30.11"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.91"Hg).
Average wind speed in December
Saint Helena, CA
- Average wind speed in December: 4.6mph
The windiest month (with the highest average wind speed) is May (5.8mph).
The calmest month (with the lowest average wind speed) is November (4.3mph).
Average humidity in December
Saint Helena, CA
- Average humidity in December: 73%
The month with the highest relative humidity is March (76%).
The month with the lowest relative humidity is September (53%).
Average rainfall in December
Saint Helena, CA
- Average rainfall in December: 2.95"
The wettest month (with the highest rainfall) is February (3.7").
The driest month (with the least rainfall) is July (0").
Average rainfall days in December
Saint Helena, CA
- Average rainfall days in December: 11.3 days
The month with the highest number of rainy days is March (13.5 days).
The month with the least rainy days is August (0.3 days).
Average snowfall in December
Saint Helena, CA
- Average snowfall in December: 0"
The month with the highest snowfall is March (0.04").
The months with the least snowfall are January, February, April, May, June, July, August, September, October, November and December (0").
Average snowfall days in December
Saint Helena, CA
- Average snowfall days in December: 0 days
The month with the highest number of snowfall days is March (0.2 days).
The months with the least snowfall days are January, February, April, May, June, July, August, September, October, November and December (0 days).
Average daylight in December /
Average sunshine in December
Saint Helena, CA
- Average daylight in December: 9h and 30min
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 30min).
- Average sunshine in December: 5h and 18min
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 18min).
Average sunshine days in December
Saint Helena, CA
- Average sunshine days in December: 19.1 days
The month with the most sunshine days is July (30 days).
The month with the least sunshine days is March (15.9 days).
Average UV index in December
Saint Helena, CA
- Average UV index in December: 3
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in December
Saint Helena, CA
- Average cloud cover in December: 42
The month with the most cloud cover is March (Cloud cover 44).
The month with the least cloud cover is July (Cloud cover 7).
Average visibility in December
Saint Helena, CA
- Average visibility in December: 6mi
The months with the highest visibility are February, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January and March (5mi).
