December weather - Winter 2024

Weather in December
Frequently asked questions
Average temperature in December
Average pressure in December
Average wind speed in December
Average humidity in December
Average rainfall in December
Average rainfall days in December
Average daylight in December
Average sunshine in December
Average sunshine days in December
Average UV index in December
Average cloud cover in December
Average visibility in December

Trees and neat lawns of the famous Muckenthaler Community Center in Fullerton, California

Weather in December

December marks the advent of winter with the lowest average temperatures recorded from 50.9°F (10.5°C) to 64°F (17.8°C). As compared to November, substantial rainfall is seen in December, going as high as 1.54" (39mm). As the temperature drops, rain increases, marking a significant change from the previous month. The comparatively colder days coupled with shorter daylight hours point to the onset of winter holidays. Brooding overcast skies may be common but that hardly takes away from the charm of Fullerton’s benign winter season.

Temperature

In Fullerton, the lowest average temperatures are observed in December, with a high of 64°F (17.8°C) and a low of 50.9°F (10.5°C).

Humidity

In December, the average relative humidity is 55%.

Rainfall

The month with the most rainfall is December, when the rain falls for 6.6 days and typically aggregates up to 1.54" (39mm) of precipitation.

Daylight

The month with the shortest days is December, with an average of 9h and 54min of daylight.
On the first day of the month, sunrise is at 6:39 am and sunset at 4:42 pm. On the last day of December, sunrise is at 6:56 am and sunset at 4:53 pm PST.

Sunshine

With an average of 6.7h of sunshine, December has the least sunshine of the year.

UV index

January, February, November and December, with an average maximum UV index of 4, are months with the lowest UV index. A UV Index value of 3 to 5 symbolizes a medium health hazard from unsafe exposure to UV radiation for average individuals.
Note: In December, the UV index of 4 transforms into the following advice:
Ensure safety - Recommendations to avert sunburn are presented. It's recommended to limit sun exposure when its radiation is at its peak during midday. Wearing sunglasses with both UVA and UVB protection effectively reduces sun-induced eye damage.

Updated: Jun 5, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate

Frequently asked questions

What are the coldest months?

In Fullerton, December records the average lowest temperatures, peaking at 64°F (17.8°C) and reaching a low of 50.9°F (10.5°C).

What are December temperatures?

The high-temperature, in December, in Fullerton, is 64°F (17.8°C), while the low-temperature averages to 50.9°F (10.5°C). The average heat index (a.k.a. 'apparent temperature', 'felt air temperature'), which factors the actual air temperature with the relative humidity, in September is computed to be 84.2°F (29°C).

What is the average humidity in December?

In Fullerton, the average relative humidity in December is 55%.

What is the wettest month?

December is the month with the most rainfall. Rain falls for 6.6 days and accumulates 1.54" (39mm) of precipitation.

How much does it rain in December?

In Fullerton, in December, during 6.6 rainfall days, 1.54" (39mm) of precipitation is typically accumulated.

What is the month with the shortest days in Fullerton?

With an average of 9h and 54min of daylight, December has the shortest days of the year.

How many hours of daylight does Fullerton have in December?

In December, the average day length is 9h and 56min.

What time are sunrise and sunset in December in Fullerton?

In December, on the first day of the month, sunrise is at 6:39 am and sunset at 4:42 pm. On the last day of the month, sunrise is at 6:56 am and sunset at 4:53 pm PST.

What is the month with the least sunshine?

With an average of 6.7h of sunshine, December has the least sunshine of the year.

How long on average sun shines in December?

The average sunshine duration in December is 6.7h.

When is the lowest UV index?

The months with the lowest UV index are January, February, November and December, with an average maximum UV index of 4.

How high is the UV index in December?

In Fullerton, the average daily maximum UV index in December is 4. A UV Index of 3 to 5 symbolizes a medium hazard to health from unsafe exposure to Sun's UV rays.

Today

Tomorrow

Long-term

Year J F M A M J J A S O N December

Nov

December

Jan

Average high temperature

71.4°F 21.9°C

64°F 17.8°C

66.2°F 19°C

Average low temperature

Average pressure

Average wind speed

Average max. wind speed

5.8mph 9.3km/h

5.7mph 9.2km/h

Average wind speed gusts

Average humidity

Average rainfall

Average rainfall days

Average daylight

Average sunshine

Average sunshine days

24.2

23.2

25.2

Average UV index

Average cloud cover

Average visibility

Average temperature in December
Fullerton, CA

Average high temperature in December: 64°F

The warmest month (with the highest average high temperature) is August (83.5°F).
The month with the lowest average high temperature is December (64°F).

Average low temperature in December: 50.9°F

The month with the highest average low temperature is August (65.5°F).
The coldest month (with the lowest average low temperature) is February (50.2°F).

Average pressure in December
Fullerton, CA

Average pressure in December: 30.07"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The month with the lowest atmospheric pressure is June (29.88"Hg).

Average wind speed in December
Fullerton, CA

Average wind speed in December: 5.1mph

The windiest month (with the highest average wind speed) is April (6mph).
The calmest months (with the lowest average wind speed) are September and October (4.7mph).

Average humidity in December
Fullerton, CA

Average humidity in December: 55%

The month with the highest relative humidity is June (65%).
The month with the lowest relative humidity is November (51%).

Average rainfall in December
Fullerton, CA

Average rainfall in December: 1.54"

The wettest month (with the highest rainfall) is December (1.54").
The driest month (with the least rainfall) is June (0.04").

Average rainfall days in December
Fullerton, CA

Average rainfall days in December: 6.6 days

The month with the highest number of rainy days is March (7.3 days).
The month with the least rainy days is June (1.5 days).

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

Average daylight in December: 9h and 5min

The month with the longest days is June (Average daylight: 14h and 24min).
The month with the shortest days is December (Average daylight: 9h and 54min).

Average sunshine in December: 6h and 4min

The months with the most sunshine are July and August (Average sunshine: 12h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 42min).

Average sunshine days in December
Fullerton, CA

Average sunshine days in December: 23.2 days

The month with the most sunshine days is August (25.8 days).
The month with the least sunshine days is February (20.6 days).

Average UV index in December
Fullerton, CA

Average UV index in December: 4

The months with the highest UV index are June, July, August and September (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 4).

Average cloud cover in December
Fullerton, CA

Average cloud cover in December: 22

The months with the most cloud cover are March and December (Cloud cover 22).
The month with the least cloud cover is August (Cloud cover 5).

Average visibility in December
Fullerton, 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).

December weather forecast
Fullerton, CA

Contents