September is one of the warmer months of the year in Twin Falls, with average highs near 25.8°C and lows around 10.3°C (mean 18.1°C). It is one of the drier months, averaging 19 mm of rainfall and 36% relative humidity across the period.
September is one of the warmer months of the year in Twin Falls. Across 45 years of records, the warmest September in Twin Falls was 2022 — when the month averaged 21.6°C — while the coldest was 1985 at 13°C. Typical September days reach 25.8°C with nights near 10.3°C. The long-term trend is warming, about 0.7°C per decade.
September is one of the drier months in Twin Falls, averaging 19 mm of rainfall. The wettest September on record was 2016 with 71 mm, while the driest was 2018 at 0 mm.
Relative humidity in Twin Falls during September averages 36%. The most humid September was 2013 at 51%, and the least humid was 1987 at 22%.
September receives about 5.3 kWh/m²/day of solar energy in Twin Falls. The sunniest Septembers were 1999, 2010 and 2011, among others at 5.7 kWh/m²/day, and the cloudiest were 2013 and 2017 at 4.6.
Average wind speed in Twin Falls during September is 2.4 m/s. The windiest Septembers were 2000 and 2013 at 2.8 m/s, while the calmest was 1990 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.3°C | 18.0°C | 18.0°C | 18.5°C | 20.0°C | +3.7°C |
| Avg High | 24.1°C | 25.7°C | 25.9°C | 25.9°C | 28.0°C | +3.9°C |
| Avg Low | 8.5°C | 10.3°C | 10.1°C | 11.0°C | 12.0°C | +3.5°C |
| Avg Rain | 20 mm | 18 mm | 13 mm | 25 mm | 17 mm | -3 mm |
September temperatures in Twin Falls have risen by about 4°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -3.1°C (1985) to a record high of 40.8°C (2022).
Rainfall in September is one of the drier months, averaging 19 mm, with a wettest year of 71 mm.
One of the best times to visit Twin Falls
September is one of the best times to visit Twin Falls. Expect days averaging 25.8°C and nights around 10.3°C (mean 18.1°C) — warmer than Twin Falls's yearly average — with low rainfall (19 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 | 28.4°C | 20.9°C | 13.5°C | 35.8°C | 7.2°C | 23 mm | 38% | 2.2 m/s | 5 |
| 2024 | 28.4°C | 20.3°C | 12.2°C | 36.9°C | 7.0°C | 14 mm | 35% | 2.2 m/s | 5.2 |
| 2023 | 26.5°C | 18.8°C | 11.2°C | 32.3°C | 5.2°C | 40 mm | 43% | 2.2 m/s | 5.1 |
| 2022 🔥 | 29.6°C | 21.6°C | 13.5°C | 40.8°C | 8.2°C | 11 mm | 29% | 2.3 m/s | 5.2 |
| 2021 | 27.3°C | 18.9°C | 10.4°C | 37.6°C | 1.7°C | 11 mm | 29% | 2.4 m/s | 5.5 |
| 2020 | 28.0°C | 19.7°C | 11.5°C | 39.1°C | 3.4°C | 3 mm | 27% | 2.5 m/s | 5.5 |
| 2019 | 24.2°C | 17.4°C | 10.5°C | 37.3°C | 0.1°C | 34 mm | 45% | 2.5 m/s | 4.8 |
| 2018 | 27.1°C | 19.1°C | 11.0°C | 34.5°C | 4.4°C | 0 mm | 23% | 2.4 m/s | 5.5 |
| 2017 | 24.4°C | 17.5°C | 10.7°C | 38.1°C | 0.4°C | 33 mm | 41% | 2.3 m/s | 4.6 |
| 2016 🌧️ | 23.3°C | 16.4°C | 9.6°C | 34.1°C | 5.2°C | 71 mm | 47% | 2.4 m/s | 4.9 |
| 2015 | 27.2°C | 19.6°C | 12.0°C | 34.0°C | 4.5°C | 18 mm | 34% | 2.2 m/s | 5.4 |
| 2014 | 25.6°C | 18.1°C | 10.6°C | 32.9°C | 1.6°C | 24 mm | 46% | 2.4 m/s | 5.2 |
| 2013 | 24.1°C | 17.6°C | 11.0°C | 35.7°C | 1.2°C | 40 mm | 51% | 2.8 m/s | 4.6 |
| 2012 | 27.9°C | 19.8°C | 11.8°C | 32.6°C | 6.8°C | 7 mm | 28% | 2.1 m/s | 5.4 |
| 2011 | 28.5°C | 20.5°C | 12.5°C | 33.4°C | 8.5°C | 8 mm | 31% | 2.1 m/s | 5.7 |
| 2010 | 26.9°C | 18.6°C | 10.2°C | 32.6°C | 3.6°C | 12 mm | 31% | 2.4 m/s | 5.7 |
| 2009 | 28.0°C | 20.2°C | 12.4°C | 34.2°C | 1.4°C | 8 mm | 30% | 2.5 m/s | 5.4 |
| 2008 | 26.2°C | 18.1°C | 9.9°C | 32.1°C | 3.3°C | 3 mm | 27% | 2.4 m/s | 5.6 |
| 2007 | 24.9°C | 17.2°C | 9.4°C | 37.3°C | -0.1°C | 22 mm | 36% | 2.6 m/s | 5.1 |
| 2006 | 24.6°C | 17.1°C | 9.5°C | 34.2°C | 1.9°C | 20 mm | 35% | 2.4 m/s | 5 |
| 2005 | 25.3°C | 17.2°C | 9.0°C | 34.7°C | 2.8°C | 10 mm | 32% | 2.4 m/s | 5.5 |
| 2004 | 24.1°C | 16.7°C | 9.3°C | 34.0°C | 3.1°C | 18 mm | 40% | 2.5 m/s | 5.3 |
| 2003 | 26.0°C | 18.2°C | 10.5°C | 33.1°C | 2.8°C | 7 mm | 31% | 2.6 m/s | 5.5 |
| 2002 | 25.6°C | 17.9°C | 10.3°C | 35.1°C | 3.3°C | 20 mm | 33% | 2.5 m/s | 5.2 |
| 2001 | 28.3°C | 19.9°C | 11.6°C | 34.6°C | 4.3°C | 17 mm | 32% | 2.5 m/s | 5.3 |
| 2000 | 25.5°C | 17.4°C | 9.4°C | 36.7°C | 1.5°C | 10 mm | 35% | 2.8 m/s | 5.4 |
| 1999 | 25.2°C | 17.0°C | 8.7°C | 31.4°C | -0.7°C | 2 mm | 25% | 2.4 m/s | 5.7 |
| 1998 | 26.5°C | 19.4°C | 12.2°C | 35.7°C | 5.2°C | 41 mm | 46% | 2.1 m/s | 5 |
| 1997 | 25.6°C | 18.4°C | 11.2°C | 33.6°C | 3.3°C | 37 mm | 47% | 2.3 m/s | 5.2 |
| 1996 | 23.7°C | 15.9°C | 8.2°C | 32.8°C | 0.3°C | 9 mm | 34% | 2.7 m/s | 5.2 |
| 1995 | 25.5°C | 18.0°C | 10.6°C | 36.5°C | 0.6°C | 12 mm | 36% | 2.4 m/s | 5.4 |
| 1994 | 27.6°C | 19.6°C | 11.6°C | 34.4°C | 8.0°C | 31 mm | 26% | 2.2 m/s | 5.4 |
| 1993 | 24.3°C | 16.6°C | 9.0°C | 32.1°C | 1.9°C | 8 mm | 31% | 2.4 m/s | 5.6 |
| 1992 | 24.9°C | 16.9°C | 8.9°C | 32.4°C | 3.7°C | 6 mm | 33% | 2.7 m/s | 5.2 |
| 1991 | 24.7°C | 17.2°C | 9.8°C | 31.9°C | 1.9°C | 28 mm | 43% | 2.2 m/s | 5.3 |
| 1990 | 29.1°C | 21.1°C | 13.1°C | 36.4°C | 8.8°C | 6 mm | 31% | 1.9 m/s | 5.5 |
| 1989 | 25.6°C | 17.3°C | 9.0°C | 32.0°C | 4.6°C | 14 mm | 32% | 2.4 m/s | 5.6 |
| 1988 | 24.4°C | 16.3°C | 8.1°C | 35.5°C | 1.0°C | 6 mm | 31% | 2.6 m/s | 5.1 |
| 1987 | 27.1°C | 18.8°C | 10.6°C | 35.8°C | 3.7°C | 1 mm | 22% | 2.2 m/s | 5.7 |
| 1986 | 20.3°C | 13.6°C | 6.9°C | 31.6°C | -1.2°C | 34 mm | 50% | 2.4 m/s | 4.7 |
| 1985 ❄️ | 20.8°C | 13.0°C | 5.2°C | 28.4°C | -3.1°C | 31 mm | 47% | 2.7 m/s | 4.9 |
| 1984 | 24.3°C | 16.1°C | 7.8°C | 34.5°C | -2.3°C | 12 mm | 37% | 2.6 m/s | 5.3 |
| 1983 | 24.6°C | 16.8°C | 9.1°C | 35.4°C | -1.5°C | 31 mm | 40% | 2.7 m/s | — |
| 1982 | 22.5°C | 15.6°C | 8.7°C | 32.9°C | 0.8°C | 50 mm | 50% | 2.6 m/s | — |
| 1981 | 27.0°C | 18.9°C | 10.8°C | 34.5°C | 1.6°C | 6 mm | 31% | 2.4 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 25.8°C with lows near 10.3°C (mean 18.1°C), based on 45 years of NASA POWER data.
September averages 19 mm of rainfall in Twin Falls, one of the drier months. The wettest on record was 71 mm in 2016.
The hottest September reached 40.8°C in 2022. The coldest dipped to -3.1°C in 1985.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 4°C. Daytime highs moved from 23.8°C to 28°C and overnight lows from 8.3°C to 12.2°C over the same span.
September is one of the warmer months of the year in Twin Falls and one of the drier months, so plan for around 25.8°C daytime highs and 10.3°C at night.
Not quite — September is the 9th coolest month in Twin Falls, averaging 18.1°C.
For September in Twin Falls, pack light layers you can adjust through the day, with typical highs of 25.8°C and lows of 10.3°C.
Relative humidity in September averages 36% — relatively dry.
Average wind speed in September is 2.4 m/s. The windiest September on record averaged 2.8 m/s (2000).
The wettest September on record was 2016 with 71 mm. On average, September sees 19 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 Twin 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.
