Climate averages 1991–2020
Boise weather
in August.
A hot, very dry month: the 2nd warmest and the 2nd driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
August is a hot month in Boise: daytime highs average 31.9°C and nights cool to about 17.4°C. By daytime temperature it is the 2nd warmest of the 12 months.
Expect about 3.3 mm of rain on fewer than one day, which makes August a very dry month (the 2nd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 59 min on an average August day.
The nearest other city in this atlas is Meridian (15 km away). In August its highs average 31.8°C, about as warm as Boise, with 3.4 mm of rain.
Among the 498 cities listed in the United States, Boise ranks joint 137th of 498 for the warmest August highs and joint 94th of 498 for the driest August (rainfall, lowest first). The mean August high of those 498 cities is 29.9°C; Boise is 2.0°C warmer than that mean.
From August to September, average highs fall by 5.8°C to 26.2°C, and monthly rainfall rises from 3.3 mm to 10 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
Boise climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 3.8°C-4.6°C | -4.6°C | 45 | 9.5 | 9.39 h |
| February | 6.8°C-2.5°C | -2.5°C | 31 | 7.7 | 10.510 h |
| March | 11.9°C0.9°C | 0.9°C | 36 | 8.9 | 11.912 h |
| April | 15.9°C3.8°C | 3.8°C | 31 | 7.2 | 13.413 h |
| May | 21.6°C8.5°C | 8.5°C | 31 | 5.9 | 14.715 h |
| June | 26.5°C13.0°C | 13.0°C | 16 | 3.2 | 15.415 h |
| July | 32.7°C17.9°C | 17.9°C | 2.6 | 0.9 | 15.115 h |
| August, selected | 31.9°C17.4°C | 17.4°C | 3.3 | 0.7 | 14.014 h |
| September | 26.2°C12.6°C | 12.6°C | 10 | 2.2 | 12.613 h |
| October | 17.7°C6.3°C | 6.3°C | 22 | 4.3 | 11.111 h |
| November | 9.3°C0.2°C | 0.2°C | 34 | 7.9 | 9.710 h |
| December | 3.7°C-4.1°C | -4.1°C | 50 | 10.1 | 9.09 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
- Meridian in AugustUnited States · 15 kmHigh 31.8°C · Low 17.4°C · 3.4 mm rain
- Nampa in AugustUnited States · 30 kmHigh 32.3°C · Low 18.3°C · 3.4 mm rain
- Kennewick in AugustUnited States · 370 kmHigh 33.0°C · Low 18.5°C · 4.2 mm rain
- Tri-Cities in AugustUnited States · 376 kmHigh 33.2°C · Low 18.6°C · 4.2 mm rain
- Missoula in AugustUnited States · 401 kmHigh 28.6°C · Low 14.9°C · 19 mm rain
- Bend in AugustUnited States · 413 kmHigh 27.2°C · Low 11.3°C · 14 mm rain
- Ogden in AugustUnited States · 437 kmHigh 30.4°C · Low 16.4°C · 11 mm rain
- Layton in AugustUnited States · 449 kmHigh 30.2°C · Low 16.4°C · 9.4 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 Boise) is explained once on the Boise year overview and on the Sources, method and limits page.