December weather forecast and climate
Saint Helena, CA

Weather in December

The first month of the winter, December, is also a fresh month in Saint Helena, California, with temperature in the range of an average high of 54.5°F (12.5°C) and an average low of 39.6°F (4.2°C).

Temperature

The coldest month is December, with an average high-temperature of 54.5°F (12.5°C) and an average low-temperature of 39.6°F (4.2°C).

Humidity

The average relative humidity in December is 73%.

Rainfall

In Saint Helena, in December, it is raining for 11.3 days, with typically 2.95" (75mm) of accumulated precipitation. In Saint Helena, during the entire year, the rain falls for 76.2 days and collects up to 16.93" (430mm) of precipitation.

Snowfall

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

Daylight

December has the shortest days of the year, with an average of 9.5h of daylight.

Sunshine

The month with the least sunshine is December, with an average of 5.3h 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 Saint Helena, California. A UV Index estimate of 3 to 5 represents a moderate health risk from unsafe exposure to the UV radiation for the ordinary person.
Note: The average daily UV index of 3 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. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.
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FAQ

What is the coldest month in Saint Helena?

With an average high-temperature of 54.5°F (12.5°C) and an average low-temperature of 39.6°F (4.2°C), December is the coldest month in Saint Helena.

What is the temperature in December in Saint Helena?

In December, the average high-temperature is 54.5°F (12.5°C), and the average low-temperature is 39.6°F (4.2°C).

What is the average humidity in December in Saint Helena?

In Saint Helena, the average relative humidity in December is 73%.

How much does it rain in Saint Helena in December?

In Saint Helena, California, in December, during 11.3 rainfall days, 2.95" (75mm) of precipitation is typically accumulated.

When it does not snow in Saint Helena?

January, February, April through December are months without snowfall in Saint Helena.

What is the month with the shortest days in Saint Helena?

The month with the shortest days is December, with an average of 9.5h of daylight.

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

The average length of the day in December is 9.5h.

What is the month with the least sunshine in Saint Helena?

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

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

In December, the average sunshine in Saint Helena, California, is 5.3h.

What are the months with the lowest UV index in Saint Helena?

Months with the lowest UV index in Saint Helena are January, February, November and December, with an average maximum UV index of 3.

What is the UV index reading in December in Saint Helena?

In December, the average daily maximum UV index in Saint Helena is 3. A UV Index value of 3 to 5 symbolizes a medium hazard to health from unsafe exposure to the Sun's UV rays.

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).

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Average pressure in December
Saint Helena, CA

Average pressure in December - Saint Helena, CA
  • Average pressure in December: 30.11"

The month with the highest atmospheric pressure is January (30.14").
Months with the lowest atmospheric pressure are June, August and September (29.91").

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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).

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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%).

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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").

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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).

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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").
Months with the least snowfall are January, February, April, May, June, July, August, September, October, November and December (0").

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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).
Months with the least snowfall days are January, February, April, May, June, July, August, September, October, November and December (0 days).

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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: 9.5h

The month with the longest days is June (Average daylight: 14.8h).
The month with the shortest days is December (Average daylight: 9.5h).

  • Average sunshine in December: 5.3h

The month with the most sunshine is July (Average sunshine: 11.9h).
The month with the least sunshine is December (Average sunshine: 5.3h).

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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).

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Average UV index in December
Saint Helena, CA

Average UV index in December - Saint Helena, CA
  • Average UV index in December: 3

Months with the highest UV index are June, July and August (UV index 6).
Months with the lowest UV index are January, February, November and December (UV index 3).

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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).

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Average visibility in December
Saint Helena, CA

Average visibility in December - Saint Helena, CA
  • Average visibility in December: 6mi

Months with the highest visibility are February, April, May, June, July, August, September, October, November and December (6mi).
Months with the lowest visibility are January and March (5mi).

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