August is one of the warmer months of the year in Helena, with average highs near 25.7°C and lows around 9.7°C (mean 17.7°C). It is about average for rainfall, averaging 39 mm of rainfall and 53% relative humidity across the period.
August is one of the warmer months of the year in Helena. Across 45 years of records, the warmest August in Helena was 2022 — when the month averaged 20.8°C — while the coldest was 1993 at 13.6°C. Typical August days reach 25.7°C with nights near 9.7°C. The long-term trend is warming, about 0.2°C per decade.
August is about average for rainfall in Helena, averaging 39 mm of rainfall. The wettest August on record was 2014 with 90 mm, while the driest was 1988 at 7 mm.
Relative humidity in Helena during August averages 53%. The most humid August was 1993 at 67%, and the least humid was 1988 at 40%.
August receives about 6 kWh/m²/day of solar energy in Helena. The sunniest August was 2001 at 6.8 kWh/m²/day, and the cloudiest were 1985 and 2021 at 5.4.
Average wind speed in Helena during August is 1.1 m/s. The windiest Augusts were 1985, 1995 and 2008 at 1.2 m/s, while the calmest was 1981 at 0.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 17.2°C | 17.5°C | 17.7°C | 17.7°C | 18.6°C | +1.4°C |
| Avg High | 25.3°C | 25.5°C | 26.0°C | 25.4°C | 26.2°C | +0.9°C |
| Avg Low | 9.2°C | 9.5°C | 9.4°C | 10.0°C | 11.1°C | +1.9°C |
| Avg Rain | 40 mm | 39 mm | 33 mm | 40 mm | 46 mm | +6 mm |
August temperatures in Helena have risen by about 0.8°C between 1981–1985 and 2021–2025.
August has ranged from a record low of -1.9°C (1992) to a record high of 35°C (1983).
Rainfall in August is about average for rainfall, averaging 39 mm, with a wettest year of 90 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.1°C per decade while lows rose 0.4°C per decade, narrowing the gap between day and night.
One of the best times to visit Helena
August is one of the best times to visit Helena. Expect days averaging 25.7°C and nights around 9.7°C (mean 17.7°C) — warmer than Helena's yearly average — with moderate rainfall (39 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 26.0°C | 18.6°C | 11.2°C | 33.4°C | 4.9°C | 48 mm | 58% | 1 m/s | 5.7 |
| 2024 | 26.4°C | 18.4°C | 10.5°C | 34.4°C | 4.4°C | 34 mm | 55% | 1 m/s | 5.6 |
| 2023 | 25.3°C | 18.3°C | 11.4°C | 33.3°C | 7.3°C | 67 mm | 60% | 1.1 m/s | 5.6 |
| 2022 🔥 | 28.6°C | 20.8°C | 13.0°C | 34.4°C | 7.5°C | 41 mm | 49% | 1 m/s | 6.3 |
| 2021 | 24.8°C | 17.2°C | 9.5°C | 31.2°C | 2.5°C | 62 mm | 56% | 1.1 m/s | 5.4 |
| 2020 | 26.0°C | 18.5°C | 11.0°C | 31.9°C | 4.8°C | 21 mm | 56% | 1.1 m/s | 6.2 |
| 2019 | 25.0°C | 17.6°C | 10.3°C | 30.7°C | 5.4°C | 49 mm | 61% | 1 m/s | 5.7 |
| 2018 | 24.0°C | 16.7°C | 9.3°C | 34.3°C | -0.2°C | 42 mm | 58% | 1 m/s | 5.8 |
| 2017 | 26.1°C | 18.3°C | 10.5°C | 30.7°C | 7.8°C | 9 mm | 49% | 1 m/s | 6.1 |
| 2016 | 25.3°C | 17.1°C | 9.0°C | 32.5°C | 4.0°C | 25 mm | 51% | 1.1 m/s | 6.3 |
| 2015 | 25.9°C | 17.9°C | 10.0°C | 32.6°C | 3.1°C | 24 mm | 52% | 1.1 m/s | 5.7 |
| 2014 🌧️ | 23.7°C | 17.0°C | 10.3°C | 31.3°C | 3.1°C | 90 mm | 63% | 1 m/s | 5.5 |
| 2013 | 28.1°C | 19.7°C | 11.4°C | 32.7°C | 8.5°C | 29 mm | 51% | 1.1 m/s | 6 |
| 2012 | 27.4°C | 18.8°C | 10.1°C | 33.4°C | 3.8°C | 25 mm | 48% | 1 m/s | 6.4 |
| 2011 | 26.1°C | 18.3°C | 10.5°C | 30.8°C | 6.6°C | 30 mm | 56% | 1 m/s | 6.5 |
| 2010 | 22.8°C | 15.5°C | 8.2°C | 30.9°C | 2.0°C | 73 mm | 63% | 1.1 m/s | 5.9 |
| 2009 | 23.9°C | 16.4°C | 9.0°C | 31.4°C | 2.9°C | 49 mm | 61% | 1.1 m/s | 5.7 |
| 2008 | 25.6°C | 17.2°C | 8.7°C | 32.6°C | 1.8°C | 33 mm | 52% | 1.2 m/s | 6.1 |
| 2007 | 26.8°C | 18.2°C | 9.6°C | 31.9°C | 5.9°C | 20 mm | 48% | 1.1 m/s | 6.1 |
| 2006 | 25.6°C | 17.3°C | 9.1°C | 32.2°C | 2.3°C | 29 mm | 49% | 1.1 m/s | 6.2 |
| 2005 | 25.2°C | 16.9°C | 8.6°C | 32.8°C | 2.7°C | 39 mm | 52% | 1.1 m/s | 6.2 |
| 2004 | 24.0°C | 16.4°C | 8.9°C | 31.6°C | 3.7°C | 65 mm | 58% | 1.1 m/s | 5.6 |
| 2003 | 29.0°C | 20.3°C | 11.7°C | 34.5°C | 4.5°C | 27 mm | 46% | 1 m/s | 6.1 |
| 2002 | 23.4°C | 15.3°C | 7.2°C | 28.3°C | 3.4°C | 50 mm | 58% | 1.1 m/s | 6 |
| 2001 | 28.9°C | 20.1°C | 11.2°C | 34.4°C | 6.9°C | 9 mm | 41% | 1 m/s | 6.8 |
| 2000 | 27.8°C | 18.8°C | 9.9°C | 33.8°C | 4.6°C | 12 mm | 41% | 1.1 m/s | 6.4 |
| 1999 | 26.1°C | 18.2°C | 10.3°C | 31.1°C | 3.2°C | 51 mm | 56% | 1.1 m/s | 5.8 |
| 1998 | 27.3°C | 19.0°C | 10.7°C | 32.4°C | 5.9°C | 22 mm | 53% | 1 m/s | 6.5 |
| 1997 | 24.0°C | 16.8°C | 9.5°C | 30.4°C | 4.9°C | 58 mm | 64% | 1 m/s | 6 |
| 1996 | 25.7°C | 17.5°C | 9.4°C | 32.8°C | 2.5°C | 25 mm | 50% | 1.1 m/s | 6.1 |
| 1995 | 25.5°C | 16.8°C | 8.1°C | 31.2°C | 2.5°C | 28 mm | 53% | 1.2 m/s | 6.3 |
| 1994 | 27.5°C | 19.0°C | 10.5°C | 32.7°C | 4.2°C | 12 mm | 47% | 1 m/s | 6 |
| 1993 ❄️ | 20.7°C | 13.6°C | 6.4°C | 28.4°C | 1.2°C | 83 mm | 67% | 1.1 m/s | 5.5 |
| 1992 | 24.4°C | 16.4°C | 8.4°C | 30.9°C | -1.9°C | 21 mm | 48% | 1.1 m/s | 6.2 |
| 1991 | 28.5°C | 19.9°C | 11.3°C | 33.3°C | 7.1°C | 18 mm | 46% | 1 m/s | 6.3 |
| 1990 | 25.4°C | 17.8°C | 10.2°C | 33.6°C | 3.7°C | 70 mm | 56% | 1 m/s | 5.7 |
| 1989 | 22.9°C | 15.6°C | 8.3°C | 29.6°C | 3.0°C | 64 mm | 59% | 1 m/s | 5.5 |
| 1988 | 26.5°C | 17.5°C | 8.5°C | 31.4°C | 3.6°C | 7 mm | 40% | 1.1 m/s | 6.4 |
| 1987 | 22.6°C | 14.6°C | 6.7°C | 30.5°C | 2.0°C | 31 mm | 55% | 1.1 m/s | 6.1 |
| 1986 | 26.0°C | 17.8°C | 9.7°C | 30.6°C | 4.0°C | 50 mm | 51% | 1 m/s | 6.1 |
| 1985 | 22.8°C | 14.7°C | 6.6°C | 30.9°C | 1.6°C | 72 mm | 54% | 1.2 m/s | 5.4 |
| 1984 | 26.4°C | 18.2°C | 10.1°C | 32.4°C | 4.4°C | 50 mm | 52% | 1.1 m/s | 5.6 |
| 1983 | 27.1°C | 19.5°C | 11.8°C | 35.0°C | 8.5°C | 43 mm | 56% | 1 m/s | — |
| 1982 | 26.0°C | 18.0°C | 10.1°C | 31.2°C | 4.9°C | 22 mm | 54% | 1.1 m/s | — |
| 1981 | 27.3°C | 19.0°C | 10.6°C | 32.2°C | 3.3°C | 21 mm | 52% | 0.9 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 25.7°C with lows near 9.7°C (mean 17.7°C), based on 45 years of NASA POWER data.
August averages 39 mm of rainfall in Helena, about average for rainfall. The wettest on record was 90 mm in 2014.
The hottest August reached 35°C in 1983. The coldest dipped to -1.9°C in 1992.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 0.8°C. Daytime highs moved from 25.9°C to 26.2°C and overnight lows from 9.8°C to 11.1°C over the same span.
August is one of the warmer months of the year in Helena and about average for rainfall, so plan for around 25.7°C daytime highs and 9.7°C at night.
Not quite — August is the 11th coolest month in Helena, averaging 17.7°C.
For August in Helena, pack light layers you can adjust through the day, with typical highs of 25.7°C and lows of 9.7°C.
Relative humidity in August averages 53% — relatively dry.
Average wind speed in August is 1.1 m/s. The windiest August on record averaged 1.2 m/s (1985).
The wettest August on record was 2014 with 90 mm. On average, August sees 39 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Helena behaves each August, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for August specifically, along with year-by-year records and how the month has changed over the decades.
