Ontario weather in December: Ontario, California: normal highs, lows, rain and records for December
Ontario in December has a normal high of 67°F and a normal low of 44°F, a daily mean of 55°F, falling from 69°F on the 1st to 67°F by the 31st. Measurable precipitation falls on 6 days in a normal December, 1.89 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 19°C and low of 6°C, 48 mm of precipitation in December.
- NOAA stationOntario International Airport
- Station IDUSW00003102
- Location34.06°N 117.60°W
- Elevation949 ft (289 m)
- From the center1 miles
- Population185,285
- Jan 68° 45°
- Feb 68° 46°
- Mar 72° 49°
- Apr 76° 51°
- May 80° 56°
- Jun 86° 60°
- Jul 94° 65°
- Aug 95° 65°
- Sep 91° 64°
- Oct 83° 57°
- Nov 75° 49°
- Dec 67° 44°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Ontario in December?
The normal high is 67°F and the normal low 44°F, for a daily mean of 55.2°F. December is 6.7°F cooler than November and 0.9°F cooler than January. December is the 12th warmest month of the year in Ontario and the 3rd wettest. Across the month the normal high falls 2°F, from 69°F on December 1 to 67°F on December 31. From one year to the next December's mean temperature typically moves about 1.9°F either way (NOAA's standard deviation), so roughly two Decembers in three average between 53°F and 57°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 18%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| December 1 | 69°F | 45°F | 16% | 9% |
| December 8 | 67°F | 44°F | 17% | 10% |
| December 15 | 66°F | 43°F | 18% | 11% |
| December 22 | 66°F | 43°F | 18% | 11% |
| December 31 | 67°F | 44°F | 17% | 11% |
Every day of December: normal high, low and chance of precipitation (warmest afternoon December 1, coldest night December 15)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| December 1 | 69°F | 45°F | 16% | 9% | 10 h |
| December 2 | 69°F | 45°F | 16% | 9% | 10 h |
| December 3 | 69°F | 45°F | 16% | 9% | 10 h |
| December 4 | 68°F | 44°F | 17% | 9% | 10 h |
| December 5 | 68°F | 44°F | 17% | 10% | 10 h |
| December 6 | 68°F | 44°F | 17% | 10% | 10 h |
| December 7 | 68°F | 44°F | 17% | 10% | 10 h |
| December 8 | 67°F | 44°F | 17% | 10% | 10 h |
| December 9 | 67°F | 44°F | 17% | 10% | 10 h |
| December 10 | 67°F | 44°F | 17% | 10% | 10 h |
| December 11 | 67°F | 44°F | 18% | 10% | 10 h |
| December 12 | 67°F | 43°F | 18% | 11% | 10 h |
| December 13 | 67°F | 43°F | 18% | 11% | 10 h |
| December 14 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 15 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 16 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 17 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 18 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 19 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 20 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 21 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 22 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 23 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 24 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 25 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 26 | 66°F | 43°F | 18% | 11% | 9 h 50 min |
| December 27 | 67°F | 44°F | 18% | 11% | 9 h 50 min |
| December 28 | 67°F | 44°F | 18% | 11% | 9 h 50 min |
| December 29 | 67°F | 44°F | 17% | 11% | 9 h 50 min |
| December 30 | 67°F | 44°F | 17% | 11% | 9 h 50 min |
| December 31 | 67°F | 44°F | 17% | 11% | 9 h 50 min |
- Normal high
- 67°FDecember average
- Normal low
- 44°FDecember average
- Precipitation
- 1.89 inmonth total
- Days with precipitation
- 60.01 inch or more
- Nights at 32°F or colder
- 1
- Daylight
- 10 h to 9 h 50 minDecember 1 to December 31
- Days at 70°F or more
- 11
- Days at 80°F or more
- 2
- Sunshine
- 85%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00003102; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Ontario in December?
On a given December day the chance of 0.01 inch or more is 17% on average, highest around December 16 (18%). In all, 1.89 in falls on 6 days of a normal December, 1 of them with an inch or more.
In a normal December in Ontario, 1 nights fall to freezing.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00003102.
What are the records for December in Ontario?
The warmest December temperature on this station's record (since 1998) is 87°F, on December 1, 2021; the coldest is 28°F, on December 23, 1998. The wettest December brought 7.82 in (2010).
The December mean against the 1991-2020 normal of 55.2°F: 2021 52.4°F (−2.8), 2022 53.4°F (−1.8), 2023 58.6°F (+3.4), 2024 58.6°F (+3.4), 2025 60.5°F (+5.3). 3 of 5 ran warmer than normal.
| December | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 52.4°F | −2.8°F | 7.36 in |
| 2022 | 53.4°F | −1.8°F | 1.64 in |
| 2023 | 58.6°F | +3.4°F | 0.98 in |
| 2024 | 58.6°F | +3.4°F | 0.00 in |
| 2025 | 60.5°F | +5.3°F | 1.93 in |
Source: records: ACIS, station USW00003102; recent months: ACIS, station USW00003102. Records and recent months use complete months only.
How does December in Ontario compare across California?
Across the 219 places PlainClimate covers in California, December normal highs run from 38°F in Tahoma to 71°F in Anaheim; Ontario's is 67°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.