Climate averages 1991–2020
Rancho Cucamonga weather
in August.
A hot, very dry month: the warmest and the driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
August is a hot month in Rancho Cucamonga: daytime highs average 33.3°C and nights cool to about 19.2°C. By daytime temperature it is the warmest month of the year.
Expect about 1.1 mm of rain on fewer than one day, which makes August a very dry month (the driest month of the year). Daylight, from sunrise to sunset, lasts about 13 h 26 min on an average August day.
The nearest other city in this atlas is Ontario (7 km away). In August its highs average 32.8°C, about as warm as Rancho Cucamonga, with almost no rain (under 1 mm).
Among the 498 cities listed in the United States, Rancho Cucamonga ranks joint 80th of 498 for the warmest August highs and joint 62nd of 498 for the driest August (rainfall, lowest first). The mean August high of those 498 cities is 29.9°C; Rancho Cucamonga is 3.4°C warmer than that mean.
From August to September, average highs fall by 1.9°C to 31.4°C, and monthly rainfall rises from 1.1 mm to 5.5 mm.
The annual picture
August 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, selected | 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 | 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
August in nearby cities
- Ontario in AugustUnited States · 7 kmHigh 32.8°C · Low 19.3°C · 0.9 mm rain
- Chino in AugustUnited States · 14 kmHigh 31.9°C · Low 18.9°C · 0.9 mm rain
- Fontana in AugustUnited States · 15 kmHigh 33.5°C · Low 19.3°C · 1.1 mm rain
- Pomona in AugustUnited States · 16 kmHigh 32.1°C · Low 18.7°C · 0.9 mm rain
- Chino Hills in AugustUnited States · 20 kmHigh 31.2°C · Low 18.4°C · 0.9 mm rain
- Riverside in AugustUnited States · 25 kmHigh 33.8°C · Low 19.7°C · 1.1 mm rain
- Corona in AugustUnited States · 26 kmHigh 33.2°C · Low 19.3°C · 1.1 mm rain
- San Bernardino in AugustUnited States · 28 kmHigh 33.9°C · Low 20.2°C · 9.0 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.