August is one of the warmer months of the year in Flagstaff, with average highs near 29.2°C and lows around 15.1°C (mean 22.2°C). It is a relatively wet time of year, averaging 69 mm of rainfall and 50% relative humidity across the period.
August is one of the warmer months of the year in Flagstaff. Across 45 years of records, the warmest August in Flagstaff was 2020 — when the month averaged 25.2°C — while the coldest was 1987 at 20.2°C. Typical August days reach 29.2°C with nights near 15.1°C. The long-term trend is warming, about 0.5°C per decade.
August is a relatively wet time of year in Flagstaff, averaging 69 mm of rainfall. The wettest August on record was 1992 with 125 mm, while the driest was 2009 at 19 mm.
Relative humidity in Flagstaff during August averages 50%. The most humid August was 1984 at 61%, and the least humid was 2002 at 32%.
August receives about 6.3 kWh/m²/day of solar energy in Flagstaff. The sunniest August was 2009 at 7 kWh/m²/day, and the cloudiest were 1986 and 2013 at 5.6.
Average wind speed in Flagstaff during August is 1.8 m/s. The windiest Augusts were 1989, 1990 and 2002 at 2.3 m/s, while the calmest were 2012 and 2022 at 1.4 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 21.2°C | 21.8°C | 22.2°C | 22.3°C | 23.8°C | +2.6°C |
| Avg High | 27.9°C | 28.8°C | 29.2°C | 29.5°C | 31.0°C | +3.1°C |
| Avg Low | 14.5°C | 14.8°C | 15.1°C | 15.2°C | 16.5°C | +2°C |
| Avg Rain | 76 mm | 70 mm | 63 mm | 73 mm | 60 mm | -17 mm |
August temperatures in Flagstaff have risen by about 2.1°C between 1981–1985 and 2021–2025.
August has ranged from a record low of 8.8°C (1989) to a record high of 36.7°C (2025).
Rainfall in August is a relatively wet time of year, averaging 69 mm, with a wettest year of 125 mm.
Daytime highs and overnight lows have shifted differently — highs rose about 0.7°C per decade while lows rose 0.4°C per decade, widening the gap between day and night.
One of the best times to visit Flagstaff
August is one of the best times to visit Flagstaff. Expect days averaging 29.2°C and nights around 15.1°C (mean 22.2°C) — warmer than Flagstaff's yearly average — with moderate rainfall (69 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 | 33.1°C | 24.9°C | 16.7°C | 36.7°C | 12.8°C | 40 mm | 35% | 2.1 m/s | 6.7 |
| 2024 | 30.6°C | 23.7°C | 16.8°C | 35.0°C | 13.6°C | 76 mm | 50% | 1.9 m/s | 6.1 |
| 2023 | 30.1°C | 23.2°C | 16.3°C | 34.3°C | 14.4°C | 80 mm | 50% | 1.9 m/s | 6.4 |
| 2022 | 28.9°C | 22.5°C | 16.1°C | 32.1°C | 13.9°C | 91 mm | 58% | 1.4 m/s | 6.2 |
| 2021 | 30.2°C | 23.0°C | 15.9°C | 35.4°C | 12.1°C | 48 mm | 49% | 2.1 m/s | 6.7 |
| 2020 🔥 | 33.2°C | 25.2°C | 17.2°C | 36.4°C | 13.5°C | 22 mm | 36% | 2.1 m/s | 6.7 |
| 2019 | 32.1°C | 24.1°C | 16.0°C | 34.9°C | 14.0°C | 19 mm | 40% | 1.9 m/s | 6.9 |
| 2018 | 30.2°C | 22.9°C | 15.7°C | 35.9°C | 11.8°C | 74 mm | 50% | 1.9 m/s | 6.3 |
| 2017 | 29.4°C | 22.2°C | 15.0°C | 33.1°C | 12.2°C | 57 mm | 49% | 1.8 m/s | 6.4 |
| 2016 | 27.6°C | 20.7°C | 13.9°C | 32.4°C | 10.2°C | 92 mm | 57% | 1.5 m/s | 6.1 |
| 2015 | 29.7°C | 22.5°C | 15.2°C | 33.8°C | 13.7°C | 101 mm | 52% | 1.8 m/s | 6.3 |
| 2014 | 27.6°C | 20.5°C | 13.4°C | 32.0°C | 10.0°C | 113 mm | 55% | 2 m/s | 6.1 |
| 2013 | 28.1°C | 21.4°C | 14.7°C | 32.2°C | 11.4°C | 96 mm | 55% | 1.6 m/s | 5.6 |
| 2012 | 30.4°C | 23.2°C | 16.1°C | 34.7°C | 12.4°C | 81 mm | 51% | 1.4 m/s | 6.2 |
| 2011 | 31.3°C | 24.0°C | 16.8°C | 34.5°C | 14.0°C | 43 mm | 44% | 1.6 m/s | 6.5 |
| 2010 | 28.6°C | 21.9°C | 15.1°C | 33.5°C | 9.2°C | 59 mm | 53% | 2.1 m/s | 6.5 |
| 2009 | 30.7°C | 22.4°C | 14.2°C | 35.2°C | 9.1°C | 19 mm | 34% | 2.1 m/s | 7 |
| 2008 | 29.1°C | 22.1°C | 15.2°C | 34.5°C | 13.0°C | 78 mm | 53% | 1.8 m/s | 6.3 |
| 2007 | 29.6°C | 22.9°C | 16.2°C | 33.8°C | 12.7°C | 74 mm | 52% | 1.7 m/s | 6.4 |
| 2006 | 27.2°C | 21.1°C | 15.0°C | 30.5°C | 11.2°C | 75 mm | 55% | 1.6 m/s | 6.2 |
| 2005 | 27.5°C | 21.0°C | 14.4°C | 32.4°C | 10.6°C | 86 mm | 57% | 1.5 m/s | 6.2 |
| 2004 | 28.0°C | 21.3°C | 14.5°C | 34.3°C | 9.9°C | 55 mm | 46% | 1.8 m/s | 6.3 |
| 2003 | 29.7°C | 22.9°C | 16.1°C | 35.7°C | 14.1°C | 69 mm | 51% | 1.7 m/s | 6.2 |
| 2002 | 31.5°C | 23.2°C | 14.9°C | 36.3°C | 11.8°C | 24 mm | 32% | 2.3 m/s | 6.8 |
| 2001 | 29.1°C | 22.2°C | 15.2°C | 34.1°C | 12.6°C | 71 mm | 49% | 1.7 m/s | 6.4 |
| 2000 | 29.6°C | 22.5°C | 15.3°C | 34.9°C | 9.5°C | 80 mm | 52% | 1.9 m/s | 5.8 |
| 1999 | 28.0°C | 21.0°C | 14.1°C | 32.4°C | 11.0°C | 69 mm | 53% | 1.7 m/s | 6.1 |
| 1998 | 29.7°C | 22.5°C | 15.2°C | 33.3°C | 12.4°C | 41 mm | 50% | 1.6 m/s | 6.5 |
| 1997 | 28.5°C | 21.9°C | 15.4°C | 32.8°C | 12.8°C | 79 mm | 54% | 1.7 m/s | 6 |
| 1996 | 30.2°C | 22.6°C | 15.0°C | 35.0°C | 10.3°C | 46 mm | 45% | 1.9 m/s | 6.8 |
| 1995 | 30.1°C | 23.1°C | 16.0°C | 35.0°C | 13.4°C | 65 mm | 49% | 1.6 m/s | 6.3 |
| 1994 | 30.6°C | 23.6°C | 16.5°C | 36.0°C | 14.4°C | 56 mm | 47% | 1.8 m/s | 6 |
| 1993 | 27.3°C | 20.5°C | 13.8°C | 34.3°C | 10.7°C | 100 mm | 55% | 2 m/s | 6 |
| 1992 🌧️ | 27.3°C | 20.9°C | 14.5°C | 32.8°C | 9.8°C | 125 mm | 58% | 1.9 m/s | 6 |
| 1991 | 28.4°C | 21.5°C | 14.7°C | 32.4°C | 12.4°C | 54 mm | 50% | 1.9 m/s | 6.3 |
| 1990 | 27.8°C | 20.4°C | 13.0°C | 32.7°C | 9.4°C | 64 mm | 48% | 2.3 m/s | 6.7 |
| 1989 | 28.0°C | 20.7°C | 13.4°C | 32.9°C | 8.8°C | 54 mm | 47% | 2.3 m/s | 6.9 |
| 1988 | 27.6°C | 21.0°C | 14.3°C | 31.6°C | 11.4°C | 103 mm | 60% | 1.7 m/s | 6.1 |
| 1987 ❄️ | 26.7°C | 20.2°C | 13.7°C | 31.1°C | 9.0°C | 75 mm | 54% | 1.8 m/s | 6.3 |
| 1986 | 28.1°C | 21.8°C | 15.4°C | 33.8°C | 12.3°C | 109 mm | 57% | 1.6 m/s | 5.6 |
| 1985 | 29.4°C | 22.0°C | 14.5°C | 32.7°C | 11.3°C | 27 mm | 45% | 1.9 m/s | 6.6 |
| 1984 | 27.1°C | 20.8°C | 14.5°C | 32.5°C | 11.7°C | 93 mm | 61% | 1.6 m/s | 6 |
| 1983 | 27.5°C | 21.0°C | 14.4°C | 31.8°C | 10.2°C | 75 mm | 59% | 1.6 m/s | — |
| 1982 | 26.8°C | 21.0°C | 15.2°C | 30.2°C | 12.2°C | 72 mm | 60% | 1.5 m/s | — |
| 1981 | 29.7°C | 22.4°C | 15.1°C | 35.5°C | 11.1°C | 76 mm | 47% | 1.8 m/s | — |
Actual recorded August data for each year, 1981–2025 — sourced from NASA POWER.
The average high in August is around 29.2°C with lows near 15.1°C (mean 22.2°C), based on 45 years of NASA POWER data.
August averages 69 mm of rainfall in Flagstaff, a relatively wet time of year. The wettest on record was 125 mm in 1992.
The hottest August reached 36.7°C in 2025. The coldest dipped to 8.8°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average August temperatures have risen by about 2.1°C. Daytime highs moved from 28.1°C to 30.6°C and overnight lows from 14.7°C to 16.4°C over the same span.
August is one of the warmer months of the year in Flagstaff and a relatively wet time of year, so plan for around 29.2°C daytime highs and 15.1°C at night.
Not quite — August is the 11th coolest month in Flagstaff, averaging 22.2°C.
For August in Flagstaff, pack light layers you can adjust through the day, with typical highs of 29.2°C and lows of 15.1°C. Bring an umbrella or light rain jacket too.
Relative humidity in August averages 50% — relatively dry.
Average wind speed in August is 1.8 m/s. The windiest August on record averaged 2.3 m/s (1989).
The wettest August on record was 1992 with 125 mm. On average, August sees 69 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 Flagstaff 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.
