September is one of the warmer months of the year in Post Falls, with average highs near 22.1°C and lows around 8.2°C (mean 15.2°C). It is one of the drier months, averaging 31 mm of rainfall and 54% relative humidity across the period.
September is one of the warmer months of the year in Post Falls. Across 45 years of records, the warmest September in Post Falls was 2025 — when the month averaged 19.7°C — while the coldest was 1985 at 10.7°C. Typical September days reach 22.1°C with nights near 8.2°C. The long-term trend is warming, about 0.7°C per decade.
September is one of the drier months in Post Falls, averaging 31 mm of rainfall. The wettest September on record was 2013 with 87 mm, while the driest was 1990 at 1 mm.
Relative humidity in Post Falls during September averages 54%. The most humid September was 1986 at 68%, and the least humid were 1987 and 2001 at 44%.
September receives about 4.4 kWh/m²/day of solar energy in Post Falls. The sunniest September was 1990 at 5.2 kWh/m²/day, and the cloudiest was 1986 at 3.5.
Average wind speed in Post Falls during September is 1 m/s. The windiest September was 1992 at 1.2 m/s, while the calmest were 2012, 2022 and 2025, among others at 0.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.4°C | 15.5°C | 15.1°C | 15.3°C | 17.2°C | +3.8°C |
| Avg High | 20.2°C | 22.7°C | 22.2°C | 22.1°C | 24.2°C | +4°C |
| Avg Low | 6.5°C | 8.3°C | 7.9°C | 8.5°C | 10.2°C | +3.7°C |
| Avg Rain | 43 mm | 25 mm | 30 mm | 30 mm | 27 mm | -16 mm |
September temperatures in Post Falls have risen by about 4.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -4.4°C (1984) to a record high of 37.9°C (1988).
Rainfall in September is one of the drier months, averaging 31 mm, with a wettest year of 87 mm.
One of the best times to visit Post Falls
September is one of the best times to visit Post Falls. Expect days averaging 22.1°C and nights around 8.2°C (mean 15.2°C) — warmer than Post Falls's yearly average — with moderate rainfall (31 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 🔥 | 27.1°C | 19.7°C | 12.3°C | 36.7°C | 5.0°C | 17 mm | 50% | 0.9 m/s | 4.4 |
| 2024 | 24.6°C | 17.6°C | 10.5°C | 35.0°C | 0.4°C | 28 mm | 54% | 1 m/s | 4.3 |
| 2023 | 22.0°C | 15.6°C | 9.2°C | 30.6°C | 3.1°C | 32 mm | 57% | 1 m/s | 4 |
| 2022 | 24.9°C | 17.7°C | 10.4°C | 35.6°C | 5.9°C | 31 mm | 52% | 0.9 m/s | 4.3 |
| 2021 | 22.5°C | 15.7°C | 8.9°C | 31.9°C | 3.9°C | 38 mm | 52% | 1.1 m/s | 4.3 |
| 2020 | 24.2°C | 17.0°C | 9.8°C | 34.4°C | 2.9°C | 18 mm | 49% | 1 m/s | 4.1 |
| 2019 | 19.7°C | 13.9°C | 8.1°C | 32.3°C | -3.6°C | 44 mm | 65% | 1 m/s | 3.6 |
| 2018 | 20.8°C | 14.2°C | 7.5°C | 30.8°C | 4.0°C | 6 mm | 51% | 1 m/s | 4.5 |
| 2017 | 22.3°C | 15.7°C | 9.0°C | 33.4°C | 1.1°C | 38 mm | 54% | 1 m/s | 3.9 |
| 2016 | 20.8°C | 14.1°C | 7.5°C | 28.5°C | 2.4°C | 26 mm | 58% | 1.1 m/s | 4.3 |
| 2015 | 21.2°C | 14.4°C | 7.6°C | 31.3°C | 3.5°C | 14 mm | 51% | 1 m/s | 4.2 |
| 2014 | 23.5°C | 16.1°C | 8.8°C | 32.1°C | 1.9°C | 25 mm | 52% | 1 m/s | 4.6 |
| 2013 🌧️ | 21.9°C | 16.0°C | 10.2°C | 34.3°C | 3.0°C | 87 mm | 65% | 1.1 m/s | 3.6 |
| 2012 | 24.5°C | 16.6°C | 8.8°C | 30.6°C | 3.5°C | 1 mm | 49% | 0.9 m/s | 5 |
| 2011 | 25.3°C | 17.3°C | 9.4°C | 33.4°C | 3.5°C | 14 mm | 49% | 1 m/s | 4.8 |
| 2010 | 20.6°C | 14.3°C | 8.0°C | 29.5°C | 2.2°C | 41 mm | 65% | 1 m/s | 4 |
| 2009 | 24.6°C | 16.9°C | 9.2°C | 33.0°C | 1.5°C | 8 mm | 48% | 1 m/s | 4.8 |
| 2008 | 22.8°C | 15.2°C | 7.6°C | 31.8°C | -0.3°C | 27 mm | 50% | 1 m/s | 4.8 |
| 2007 | 21.6°C | 14.5°C | 7.3°C | 30.1°C | 0.1°C | 15 mm | 52% | 1 m/s | 4.7 |
| 2006 | 23.0°C | 15.5°C | 8.1°C | 34.5°C | 1.9°C | 26 mm | 50% | 0.9 m/s | 4.5 |
| 2005 | 20.0°C | 13.6°C | 7.1°C | 28.0°C | 1.5°C | 44 mm | 52% | 1 m/s | 4.4 |
| 2004 | 19.5°C | 13.5°C | 7.5°C | 26.7°C | 2.7°C | 47 mm | 66% | 1 m/s | 3.9 |
| 2003 | 23.2°C | 16.0°C | 8.9°C | 34.6°C | 3.0°C | 36 mm | 50% | 1.1 m/s | 4.5 |
| 2002 | 22.1°C | 14.9°C | 7.6°C | 33.2°C | 1.9°C | 19 mm | 49% | 1 m/s | 4.4 |
| 2001 | 25.3°C | 17.4°C | 9.4°C | 32.5°C | 3.0°C | 12 mm | 44% | 1 m/s | 4.9 |
| 2000 | 19.9°C | 13.3°C | 6.6°C | 33.8°C | -4.4°C | 65 mm | 60% | 1.1 m/s | 3.7 |
| 1999 | 22.3°C | 14.6°C | 6.8°C | 29.0°C | -1.6°C | 5 mm | 45% | 1.1 m/s | 4.9 |
| 1998 | 25.2°C | 18.2°C | 11.2°C | 34.1°C | 5.6°C | 32 mm | 52% | 1 m/s | 4.7 |
| 1997 | 22.4°C | 15.5°C | 8.6°C | 31.0°C | 2.4°C | 52 mm | 64% | 1.1 m/s | 4.1 |
| 1996 | 18.8°C | 12.6°C | 6.4°C | 32.7°C | -0.8°C | 30 mm | 63% | 1 m/s | 4 |
| 1995 | 22.4°C | 15.6°C | 8.8°C | 33.6°C | 0.6°C | 57 mm | 58% | 1 m/s | 4.5 |
| 1994 | 24.5°C | 17.1°C | 9.7°C | 31.6°C | 5.2°C | 20 mm | 45% | 1 m/s | 4.6 |
| 1993 | 21.4°C | 14.2°C | 7.1°C | 29.1°C | 2.5°C | 11 mm | 56% | 1 m/s | 4.9 |
| 1992 | 19.6°C | 12.9°C | 6.1°C | 28.5°C | 1.6°C | 43 mm | 57% | 1.2 m/s | 4.3 |
| 1991 | 23.6°C | 15.9°C | 8.2°C | 29.5°C | 1.9°C | 4 mm | 48% | 1 m/s | 4.9 |
| 1990 | 26.4°C | 18.4°C | 10.3°C | 31.6°C | 6.8°C | 1 mm | 47% | 0.9 m/s | 5.2 |
| 1989 | 22.7°C | 15.1°C | 7.4°C | 29.3°C | 3.4°C | 22 mm | 52% | 1 m/s | 5 |
| 1988 | 22.0°C | 14.6°C | 7.3°C | 37.9°C | 0.0°C | 34 mm | 50% | 1.1 m/s | 4.1 |
| 1987 | 24.6°C | 16.9°C | 9.2°C | 33.1°C | 2.1°C | 7 mm | 44% | 1 m/s | 5 |
| 1986 | 16.6°C | 11.0°C | 5.5°C | 28.3°C | 1.2°C | 83 mm | 68% | 1 m/s | 3.5 |
| 1985 ❄️ | 16.9°C | 10.7°C | 4.4°C | 23.7°C | -4.0°C | 79 mm | 64% | 1.1 m/s | 3.9 |
| 1984 | 18.8°C | 12.0°C | 5.2°C | 29.2°C | -4.4°C | 51 mm | 58% | 1.1 m/s | 4.2 |
| 1983 | 18.0°C | 11.5°C | 5.0°C | 24.7°C | -2.1°C | 29 mm | 62% | 1.1 m/s | — |
| 1982 | 20.2°C | 13.5°C | 6.8°C | 30.6°C | -0.3°C | 57 mm | 62% | 1 m/s | — |
| 1981 | 21.9°C | 14.9°C | 7.9°C | 34.3°C | 0.6°C | 29 mm | 53% | 1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 22.1°C with lows near 8.2°C (mean 15.2°C), based on 45 years of NASA POWER data.
September averages 31 mm of rainfall in Post Falls, one of the drier months. The wettest on record was 87 mm in 2013.
The hottest September reached 37.9°C in 1988. The coldest dipped to -4.4°C in 1984.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 4.8°C. Daytime highs moved from 19.2°C to 24.2°C and overnight lows from 5.9°C to 10.3°C over the same span.
September is one of the warmer months of the year in Post Falls and one of the drier months, so plan for around 22.1°C daytime highs and 8.2°C at night.
Not quite — September is the 10th coolest month in Post Falls, averaging 15.2°C.
For September in Post Falls, pack light layers you can adjust through the day, with typical highs of 22.1°C and lows of 8.2°C.
Relative humidity in September averages 54% — relatively dry.
Average wind speed in September is 1 m/s. The windiest September on record averaged 1.2 m/s (1992).
The wettest September on record was 2013 with 87 mm. On average, September sees 31 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 Post Falls behaves each September, 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 September specifically, along with year-by-year records and how the month has changed over the decades.
