Climate averages 1991–2020
Rancho Cucamonga weather
in December.
A mild, moderately wet month: the coolest and the 9th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
December is a mild month in Rancho Cucamonga: daytime highs average 16.9°C and nights cool to about 5.4°C. By daytime temperature it is the coolest month of the year.
Expect about 67 mm of rain on roughly 6 days, which makes December a moderately wet month (the 9th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 9 h 56 min on an average December day.
The nearest other city in this atlas is Ontario (7 km away). In December its highs average 17.2°C, about as warm as Rancho Cucamonga, with 62 mm of rain.
Among the 498 cities listed in the United States, Rancho Cucamonga ranks joint 113th of 498 for the warmest December highs and joint 245th of 498 for the driest December (rainfall, lowest first). The mean December high of those 498 cities is 10.5°C; Rancho Cucamonga is 6.3°C warmer than that mean.
From December to January, average highs rise by 0.3°C to 17.2°C, and monthly rainfall rises from 67 mm to 96 mm.
The annual picture
December in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Rancho Cucamonga climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 17.2°C5.6°C | 5.6°C | 96 | 6.6 | 10.210 h |
| February | 17.5°C6.1°C | 6.1°C | 111 | 7.4 | 10.911 h |
| March | 19.5°C7.7°C | 7.7°C | 68 | 6.8 | 12.012 h |
| April | 22.0°C9.4°C | 9.4°C | 32 | 4.6 | 13.013 h |
| May | 24.8°C12.2°C | 12.2°C | 15 | 2.6 | 13.914 h |
| June | 28.9°C15.3°C | 15.3°C | 3.4 | 0.5 | 14.414 h |
| July | 32.3°C18.7°C | 18.7°C | 2.2 | 0.5 | 14.214 h |
| August | 33.3°C19.2°C | 19.2°C | 1.1 | 0.3 | 13.413 h |
| September | 31.4°C17.4°C | 17.4°C | 5.5 | 1.2 | 12.412 h |
| October | 26.4°C13.2°C | 13.2°C | 22 | 3.1 | 11.411 h |
| November | 21.3°C8.8°C | 8.8°C | 30 | 3.5 | 10.410 h |
| December, selected | 16.9°C5.4°C | 5.4°C | 67 | 5.8 | 9.910 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
December in nearby cities
- Ontario in DecemberUnited States · 7 kmHigh 17.2°C · Low 6.1°C · 62 mm rain
- Chino in DecemberUnited States · 14 kmHigh 17.2°C · Low 5.2°C · 62 mm rain
- Fontana in DecemberUnited States · 15 kmHigh 16.3°C · Low 4.1°C · 67 mm rain
- Pomona in DecemberUnited States · 16 kmHigh 17.3°C · Low 6.1°C · 62 mm rain
- Chino Hills in DecemberUnited States · 20 kmHigh 16.9°C · Low 5.1°C · 62 mm rain
- Riverside in DecemberUnited States · 25 kmHigh 17.1°C · Low 4.5°C · 67 mm rain
- Corona in DecemberUnited States · 26 kmHigh 18.0°C · Low 5.6°C · 67 mm rain
- San Bernardino in DecemberUnited States · 28 kmHigh 16.5°C · Low 4.5°C · 55 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Rancho Cucamonga) is explained once on the Rancho Cucamonga year overview and on the Sources, method and limits page.
Riverside, Fontana and Corona lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.