Climate averages 1991–2020
San Bernardino weather
in August.
A hot, very dry month: the warmest and the 3rd driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
August is a hot month in San Bernardino: daytime highs average 33.9°C and nights cool to about 20.2°C. By daytime temperature it is the warmest month of the year.
Expect about 9.0 mm of rain on roughly 3 days, which makes August a very dry month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 26 min on an average August day.
The nearest other city in this atlas is Redlands (11 km away). In August its highs average 34.0°C, about as warm as San Bernardino, with 9.0 mm of rain.
Among the 498 cities listed in the United States, San Bernardino ranks joint 68th of 498 for the warmest August highs and joint 108th of 498 for the driest August (rainfall, lowest first). The mean August high of those 498 cities is 29.9°C; San Bernardino is 4.0°C warmer than that mean.
From August to September, average highs fall by 2.0°C to 31.9°C, and monthly rainfall falls from 9.0 mm to 7.8 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
San Bernardino climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 16.9°C4.7°C | 4.7°C | 74 | 6.1 | 10.210 h |
| February | 17.3°C5.4°C | 5.4°C | 92 | 6.8 | 10.911 h |
| March | 19.5°C7.1°C | 7.1°C | 56 | 6.2 | 12.012 h |
| April | 22.2°C9.1°C | 9.1°C | 28 | 3.9 | 13.013 h |
| May | 25.2°C12.2°C | 12.2°C | 13 | 2.6 | 13.914 h |
| June | 29.5°C15.7°C | 15.7°C | 3.5 | 0.7 | 14.414 h |
| July | 32.9°C19.6°C | 19.6°C | 12 | 2.6 | 14.214 h |
| August, selected | 33.9°C20.2°C | 20.2°C | 9.0 | 2.8 | 13.413 h |
| September | 31.9°C17.5°C | 17.5°C | 7.8 | 1.8 | 12.412 h |
| October | 26.6°C12.6°C | 12.6°C | 18 | 2.4 | 11.411 h |
| November | 21.1°C7.9°C | 7.9°C | 25 | 3.1 | 10.410 h |
| December | 16.5°C4.5°C | 4.5°C | 55 | 5.0 | 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
- Redlands in AugustUnited States · 11 kmHigh 34.0°C · Low 20.2°C · 9.0 mm rain
- Fontana in AugustUnited States · 13 kmHigh 33.5°C · Low 19.3°C · 1.1 mm rain
- Moreno Valley in AugustUnited States · 20 kmHigh 32.9°C · Low 20.0°C · 9.0 mm rain
- Riverside in AugustUnited States · 20 kmHigh 33.8°C · Low 19.7°C · 1.1 mm rain
- Rancho Cucamonga in AugustUnited States · 28 kmHigh 33.3°C · Low 19.2°C · 1.1 mm rain
- Ontario in AugustUnited States · 34 kmHigh 32.8°C · Low 19.3°C · 0.9 mm rain
- Hesperia in AugustUnited States · 35 kmHigh 33.7°C · Low 18.6°C · 6.0 mm rain
- Corona in AugustUnited States · 36 kmHigh 33.2°C · Low 19.3°C · 1.1 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 San Bernardino) is explained once on the San Bernardino year overview and on the Sources, method and limits page.
Moreno Valley and Redlands lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.