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Rancho Cucamonga Weather by Month
Average temperatures, rainfall and humidity for Rancho Cucamonga, United States, month by month, built from OpenWeather's historical records. Use it to see what a typical Rancho Cucamonga month looks like before you travel — then check the live Rancho Cucamonga forecast for the days ahead.
Warmest month
August
33°C average high
Coolest month
January
8°C average low
Wettest month
December
50 mm of rain
Driest month
June
2 mm of rain
Average temperature and rainfall in Rancho Cucamonga by month
Averages of the daily highs and lows recorded in each month, with total rainfall, mean humidity and mean wind speed.
| Month | Avg high | Avg low | Record low / high | Rainfall | Humidity | Wind |
|---|---|---|---|---|---|---|
| January | 19°C | 8°C | -9°C / 30°C | 46 mm | 54% | 9 km/h |
| February | 20°C | 8°C | -5°C / 33°C | 50 mm | 56% | 9 km/h |
| March | 22°C | 9°C | -23°C / 37°C | 38 mm | 59% | 10 km/h |
| April | 24°C | 11°C | -2°C / 36°C | 16 mm | 57% | 11 km/h |
| May | 25°C | 13°C | 3°C / 38°C | 21 mm | 62% | 11 km/h |
| June | 30°C | 16°C | 8°C / 43°C | 2 mm | 58% | 11 km/h |
| July | 33°C | 19°C | 10°C / 44°C | 5 mm | 53% | 11 km/h |
| August | 33°C | 19°C | 9°C / 41°C | 4 mm | 52% | 10 km/h |
| September | 31°C | 18°C | 5°C / 46°C | 8 mm | 54% | 9 km/h |
| October | 27°C | 13°C | 1°C / 40°C | 11 mm | 52% | 8 km/h |
| November | 23°C | 10°C | -4°C / 34°C | 21 mm | 49% | 8 km/h |
| December | 19°C | 8°C | -6°C / 30°C | 50 mm | 56% | 8 km/h |
Best time to visit Rancho Cucamonga
The most comfortable time to visit Rancho Cucamonga is generally April to May and November, balancing mild daytime temperatures against the driest stretch of the year. The city has a moderate seasonal swing and rain concentrates around December, totalling about 272 mm a year.
Travellers who prefer heat should aim for August, when highs average 33°C. December is the month to avoid if rain would spoil your plans — it averages 50 mm, roughly 30× the rainfall of June.
Source: OpenWeather historical and statistical weather data. Values are long-term averages, not a forecast — see the Rancho Cucamonga forecast for what is happening now.