December weather forecastRialto, CA
December
Weather in December
December, the first month of the winter in Rialto, is still a mild month, with an average temperature fluctuating between 59.9°F (15.5°C) and 43.5°F (6.4°C).Temperature
In Rialto, California, December records the lowest average temperatures, peaking at 59.9°F (15.5°C) and reaching a low of 43.5°F (6.4°C).Humidity
The average relative humidity in December is 51%.Rainfall
The months with the most rainfall in Rialto are February and December, with an average 1.14" (29mm) of precipitation.Snowfall
January, March through December are months without snowfall in Rialto.Daylight
The month with the shortest days is December, with an average of 9h and 54min of daylight.On the first day of December in Rialto, sunrise is at 6:37 am and sunset at 4:40 pm. On the last day of the month, sunrise is at 6:55 am and sunset at 4:50 pm PST.
Sunshine
With an average of 6.9h of sunshine, December has the least sunshine of the year in Rialto, California.UV index
December is the month with the lowest UV index, 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 average person.Note: A maximum high UV index of 3 in December translates into the following recommendations:
Exercise prudence. Persons with fair skin could be burned in under 30 minutes. Avoiding direct sun during mid-day hours can prevent harmful UV radiation exposure. 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
Rialto, CA
- Average high temperature in December: 59.9°F
The warmest month (with the highest average high temperature) is August (91.9°F).
The month with the lowest average high temperature is December (59.9°F).
- Average low temperature in December: 43.5°F
The month with the highest average low temperature is August (65.8°F).
The coldest month (with the lowest average low temperature) is February (43.3°F).
Average pressure in December
Rialto, 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 (29.85"Hg).
Average wind speed in December
Rialto, CA
- Average wind speed in December: 5.3mph
The windiest month (with the highest average wind speed) is April (6.2mph).
The calmest month (with the lowest average wind speed) is September (4.5mph).
Average humidity in December
Rialto, CA
- Average humidity in December: 51%
The months with the highest relative humidity are February and March (52%).
The month with the lowest relative humidity is August (38%).
Average rainfall in December
Rialto, CA
- Average rainfall in December: 1.14"
The wettest months (with the highest rainfall) are February and December (1.14").
The driest month (with the least rainfall) is June (0.04").
Average rainfall days in December
Rialto, CA
- Average rainfall days in December: 5.5 days
The month with the highest number of rainy days is December (5.5 days).
The month with the least rainy days is June (1.3 days).
Average snowfall days in December
Rialto, CA
- Average snowfall days in December: 0 days
The month with the highest number of snowfall days is February (0.1 days).
The months with the least snowfall days are January, March, April, May, June, July, August, September, October, November and December (0 days).
Average daylight in December /
Average sunshine in December
Rialto, CA
- Average daylight in December: 9h and 54min
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 54min
The months with the most sunshine are June and July (Average sunshine: 12h and 6min).
The month with the least sunshine is December (Average sunshine: 6h and 54min).
Average sunshine days in December
Rialto, CA
- Average sunshine days in December: 24.5 days
The month with the most sunshine days is June (27.8 days).
The month with the least sunshine days is February (22.6 days).
Average UV index in December
Rialto, CA
- Average UV index in December: 3
The months with the highest UV index are June, July and August (UV index 7).
The month with the lowest UV index is December (UV index 3).
Average cloud cover in December
Rialto, CA
- Average cloud cover in December: 21
The month with the most cloud cover is December (Cloud cover 21).
The month with the least cloud cover is August (Cloud cover 5).
Average visibility in December
Rialto, 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).
