December weather forecastPortola, CA
December
Weather in December
December, the first month of the winter in Portola, is also an icy month, with temperature in the range of an average low of 21.6°F (-5.8°C) and an average high of 37.2°F (2.9°C).Temperature
Portola's temperature records reveal December as the coldest month, marked by average highs of 37.2°F (2.9°C) and lows of 21.6°F (-5.8°C).Humidity
In December, the average relative humidity is 79%.Rainfall
In December, the rain falls for 6.8 days. Throughout December, 3.66" (93mm) of precipitation is accumulated. In Portola, during the entire year, the rain falls for 80.1 days and collects up to 22.95" (583mm) of precipitation.Snowfall
January through June, September through December are months with snowfall in Portola, California. December is the month with the most snowfall. Snow falls for 12.8 days and accumulates 22.52" (572mm) of snow.Daylight
With an average of 9h and 24min of daylight, December has the shortest days of the year.On the first day of the month, sunrise is at 7:04 am and sunset at 4:37 pm. On the last day of December, sunrise is at 7:23 am and sunset at 4:47 pm PST.
Sunshine
In December, the average sunshine is 5.2h.UV index
In Portola, the average daily maximum UV index in December is 2. A UV Index estimate of 2, and below, represents a minimal health hazard from exposure to the Sun's UV radiation for ordinary individuals.Note: A maximum high daily UV index of 2 during December translates into the following directions:
Children necessitate constant protection from sunlight, unlike the majority, who can remain under the sun for about an hour without burning. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. Experience reduced UV exposure by about half when donning a wide-brim hat. Take note! UV radiation from the Sun can double in intensity due to snow reflection.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in December
Portola, CA
- Average high temperature in December: 37.2°F
The warmest month (with the highest average high temperature) is July (82.9°F).
The month with the lowest average high temperature is December (37.2°F).
- Average low temperature in December: 21.6°F
The month with the highest average low temperature is July (47.5°F).
The coldest month (with the lowest average low temperature) is December (21.6°F).
Average pressure in December
Portola, CA
- Average pressure in December: 30.16"Hg
The month with the highest atmospheric pressure is January (30.19"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).
Average wind speed in December
Portola, CA
- Average wind speed in December: 5.7mph
The windiest month (with the highest average wind speed) is March (6.6mph).
The calmest months (with the lowest average wind speed) are August and September (5.2mph).
Average humidity in December
Portola, CA
- Average humidity in December: 79%
The months with the highest relative humidity are January and March (81%).
The months with the lowest relative humidity are July and August (40%).
Average rainfall in December
Portola, CA
- Average rainfall in December: 3.66"
The wettest month (with the highest rainfall) is March (4.02").
The driest month (with the least rainfall) is August (0.2").
Average rainfall days in December
Portola, CA
- Average rainfall days in December: 6.8 days
The month with the highest number of rainy days is May (11.8 days).
The month with the least rainy days is July (3.3 days).
Average snowfall in December
Portola, CA
- Average snowfall in December: 22.52"
The month with the highest snowfall is December (22.52").
The months with the least snowfall are July and August (0").
Average snowfall days in December
Portola, CA
- Average snowfall days in December: 12.8 days
The month with the highest number of snowfall days is March (14.7 days).
The months with the least snowfall days are July and August (0 days).
Average daylight in December /
Average sunshine in December
Portola, CA
- Average daylight in December: 9h and 24min
The month with the longest days is June (Average daylight: 14h and 54min).
The month with the shortest days is December (Average daylight: 9h and 24min).
- Average sunshine in December: 5h and 12min
The month with the most sunshine is July (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 5h and 0min).
Average sunshine days in December
Portola, CA
- Average sunshine days in December: 15.5 days
The month with the most sunshine days is August (26 days).
The month with the least sunshine days is March (11.8 days).
Average UV index in December
Portola, CA
- Average UV index in December: 2
The months with the highest UV index are June, July and August (UV index 5).
The month with the lowest UV index is November (UV index 1).
Average cloud cover in December
Portola, CA
- Average cloud cover in December: 45
The month with the most cloud cover is March (Cloud cover 47).
The month with the least cloud cover is July (Cloud cover 7).
Average visibility in December
Portola, CA
- Average visibility in December: 4mi
The months with the highest visibility are May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January and December (4mi).
