Ontario, CA weather in December
In December, Ontario sees highs around 67°F and lows around 44°F: mild and mostly dry. Rain falls on about 6 days. It is one of the coolest months in Ontario. Good for outdoor plans.
- Normal high
- 67°F
- Normal low
- 44°F
- Wet days
- 6
- 1.9 in total
- Muggy days
- 0
- dew point 65°F+
How December changes from start to finish
| December 1 | December 31 | |
|---|---|---|
| Normal high | 69°F | 67°F |
| Normal low | 45°F | 44°F |
| Chance of a wet day | 17% | 18% |
| Sunrise / sunset | 6:38 am / 4:41 pm | 6:55 am / 4:51 pm |
| Daylight | 10.1 h | 9.9 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Pacific Time).
A typical December day
- 6 am42°Fdew point 32°F
- 9 am52°Fdew point 34°F
- Noon63°Fdew point 30°F
- 3 pm64°Fdew point 30°F
- 6 pm54°Fdew point 33°F
- 9 pm49°Fdew point 33°F
NOAA hourly normals (local standard time) from March AFB (26 mi away); average wind 5 mph; clear or few clouds in 61% of daytime hours, mostly cloudy or overcast in 31%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F15 of 31
- Hot dayshigh 90°F or more0 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow6 of 31
- Notable rainat least 0.10 in3 of 31
- Freezing nightslow 32°F or below1 of 31
Average days per December, counted from daily records for each year 1991-2020.
Rain in December
Normal precipitation is 1.9 in; a dry December brings about 0.6 in and a wet one about 2.9 in (25th and 75th percentiles). About 1 day brings half an inch or more, and about 1 an inch or more. Snow is very rare.
How December varies from year to year
- Warmest December, 1991-20202017: average high 75°F
- Coolest December2001: average high 63°F
- Wettest December2010: 7.8 in
- Driest December2017: no measurable precipitation
- Highest reading86°F (December 24, 2005)
- Lowest reading28°F (December 23, 1998)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
December compared with November and January
| November | December | January | |
|---|---|---|---|
| Normal high | 75°F | 67°F | 68°F |
| Normal low | 49°F | 44°F | 45°F |
| Wet days | 4 | 6 | 5 |
| Comfortable days | 18 | 15 | 16 |
| Daylight | 10.4 h | 9.9 h | 10.2 h |
Highs change by -8°F from November and +1°F into January.
Nearby alternatives in December
- Drier: Palm Springs, CA65 mi · high 69°F · 2 wet days
- Cooler: Victorville, CA39 mi · high 57°F · 4 wet days
How Ontario ranks in December
- Normal high50th warmest of 378 cities; 15th of 60 in California
- Wet days62nd driest of 378
- Comfortable days32nd most of 340
Heating and cooling
December has 304 heating degree days and 2 cooling degree days (base 65°F), 9% of the year's total heating and cooling demand.
Questions
How cold is Ontario in December?
The normal high is 67°F and the normal low is 44°F. From 1991 to 2020 the coldest December reading was 28°F (most recently on December 23, 1998).
Does it rain a lot in Ontario in December?
About 6 days in December have at least 0.01 in of precipitation, and the normal total is 1.9 in. The wettest December in 1991-2020 was in 2010 (7.8 in); the driest was in 2017, with no measurable precipitation.
Is December a good time to visit Ontario?
December ranks 7th of 12 months on our comfort score for Ontario (64 out of 100). It has about 15 comfortable days. The best months are March, April and May.
Where the numbers come from
- Temperature, rain and frost dates: Ontario Intl Airport (USW00003102), 2.9 mi E of the city center, 949 ft (52 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Snowfall and snow depth: San Gabriel Canyon PH (USC00047776), 16 mi WNW of the city center, 744 ft (257 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour and cloud cover: March AFB (USW00023119), 26 mi ESE of the city center, 1,516 ft (515 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: March Air Reserve Base (722860-23119), 26 mi ESE of the city center, 1,536 ft (535 ft higher than the city). Hourly observations, 1991-2020.