December weather forecast
Saint Helena, CA

Share

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.

Frequently asked questions

What part of the year is the coldest?

Temperature readings reach their annual highs in December, averaging 54.5°F (12.5°C) and a minimum average of 39.6°F (4.2°C).

What is the temperature in December?

An average high-temperature, in December, in Saint Helena, is 54.5°F (12.5°C) and the average low-temperature is 39.6°F (4.2°C). The average heat index (a.k.a. 'apparent temperature', 'real feel'), which takes the relative humidity and factors it into the air temperature reading, in September is appraised at 87.8°F (31°C).

What is the average humidity in December?

The average relative humidity in December is 73%.

How many days does it rain in December?

In December, the rain falls for 11.3 days. Throughout December, 2.95" (75mm) of precipitation is accumulated.

When it does not snow?

January, February, April through December are months without snowfall.

What is the month with the shortest days?

The month with the shortest days is December, with an average of 9h and 30min of daylight.

What is the average length of the day in December?

In Saint Helena, the average day length in December is 9h and 32min.

When is the sunrise / sunset in December?

On the first day of December, sunrise is at 7:09 am and sunset at 4:49 pm. On the last day of the month, sunrise is at 7:27 am and sunset at 4:59 pm PST.

What is the month with the least sunshine?

December has the least sunshine of the year, with an average of 5.3h of sunshine.

How many hours of sunshine does Saint Helena have in December?

In December, the average sunshine duration is 5.3h.

When is the lowest UV index in Saint Helena?

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

How high is the UV index in December in Saint Helena?

The average daily maximum UV index in December is 3. A UV Index of 3 to 5 symbolizes a medium hazard to health from exposure to the Sun's UV radiation.
Average max. wind speed
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in December
Saint Helena, CA

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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 / Average sunshine in December - Saint Helena, CA
  • Average daylight in December: 9h and 3min

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 2min

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 - 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 - 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 - 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 - 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).

Saint Helena, California, USA

Weather forecast for your location

1. Click Locate me button
2. Allow the app to use your location