September is one of the warmer months of the year in Ithaca, with average highs near 22.2°C and lows around 10.5°C (mean 16.4°C). It is a relatively wet time of year, averaging 98 mm of rainfall and 74% relative humidity across the period.
September is one of the warmer months of the year in Ithaca. Across 45 years of records, the warmest September in Ithaca was 2015 — when the month averaged 19.5°C — while the coldest was 1984 at 14°C. Typical September days reach 22.2°C with nights near 10.5°C. The long-term trend is warming, about 0.5°C per decade.
September is a relatively wet time of year in Ithaca, averaging 98 mm of rainfall. The wettest September on record was 2011 with 248 mm, while the driest was 2017 at 48 mm.
Relative humidity in Ithaca during September averages 74%. The most humid September was 2011 at 86%, and the least humid was 1983 at 62%.
September receives about 4 kWh/m²/day of solar energy in Ithaca. The sunniest September was 2016 at 4.8 kWh/m²/day, and the cloudiest was 1993 at 3.2.
Average wind speed in Ithaca during September is 0.2 m/s. The windiest Septembers were 2023, 2024 and 2025, among others at 0.2 m/s, while the calmest were 1981 and 2011 at 0.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 15.7°C | 15.5°C | 16.6°C | 17.2°C | 17.0°C | +1.3°C |
| Avg High | 21.6°C | 21.4°C | 22.4°C | 23.0°C | 22.7°C | +1.1°C |
| Avg Low | 9.7°C | 9.7°C | 10.7°C | 11.2°C | 11.3°C | +1.6°C |
| Avg Rain | 93 mm | 98 mm | 99 mm | 107 mm | 85 mm | -8 mm |
September temperatures in Ithaca have risen by about 1.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -2.7°C (1991) to a record high of 33.8°C (2002).
Rainfall in September is a relatively wet time of year, averaging 98 mm, with a wettest year of 248 mm.
One of the best times to visit Ithaca
September is one of the best times to visit Ithaca. Expect days averaging 22.2°C and nights around 10.5°C (mean 16.4°C) — warmer than Ithaca's yearly average — with higher rainfall (98 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 | 24.2°C | 17.7°C | 11.2°C | 27.3°C | 5.9°C | 55 mm | 70% | 0.2 m/s | 4.6 |
| 2024 | 23.5°C | 17.8°C | 12.1°C | 28.5°C | 6.6°C | 79 mm | 76% | 0.2 m/s | 4.3 |
| 2023 | 23.0°C | 17.2°C | 11.4°C | 32.8°C | 6.0°C | 66 mm | 78% | 0.2 m/s | 4.3 |
| 2022 | 21.0°C | 16.1°C | 11.2°C | 27.8°C | 1.7°C | 148 mm | 81% | 0.2 m/s | 3.7 |
| 2021 | 21.7°C | 16.5°C | 11.2°C | 26.7°C | 5.0°C | 110 mm | 82% | 0.2 m/s | 3.9 |
| 2020 | 22.9°C | 16.7°C | 10.5°C | 30.3°C | 0.5°C | 52 mm | 70% | 0.2 m/s | 4.2 |
| 2019 | 23.5°C | 17.2°C | 10.9°C | 30.0°C | 6.4°C | 52 mm | 74% | 0.2 m/s | 4.2 |
| 2018 | 23.1°C | 18.2°C | 13.3°C | 31.1°C | 5.5°C | 158 mm | 82% | 0.2 m/s | 3.8 |
| 2017 | 23.7°C | 17.7°C | 11.6°C | 32.4°C | 5.3°C | 48 mm | 75% | 0.2 m/s | 4.2 |
| 2016 | 25.0°C | 18.4°C | 11.8°C | 33.2°C | 4.3°C | 62 mm | 68% | 0.2 m/s | 4.8 |
| 2015 🔥 | 25.8°C | 19.5°C | 13.1°C | 33.3°C | 6.6°C | 98 mm | 68% | 0.2 m/s | 4.3 |
| 2014 | 22.6°C | 16.2°C | 9.8°C | 29.8°C | 2.0°C | 54 mm | 74% | 0.2 m/s | 4.3 |
| 2013 | 20.5°C | 14.4°C | 8.2°C | 29.9°C | 1.4°C | 101 mm | 77% | 0.2 m/s | 4.3 |
| 2012 | 22.0°C | 16.2°C | 10.4°C | 29.3°C | 4.6°C | 100 mm | 73% | 0.2 m/s | 3.9 |
| 2011 🌧️ | 21.7°C | 17.0°C | 12.3°C | 31.5°C | 3.2°C | 248 mm | 86% | 0.1 m/s | 3.4 |
| 2010 | 22.3°C | 16.7°C | 11.0°C | 32.4°C | 4.9°C | 148 mm | 72% | 0.2 m/s | 3.6 |
| 2009 | 21.1°C | 15.5°C | 10.0°C | 25.8°C | 2.8°C | 69 mm | 77% | 0.2 m/s | 4.1 |
| 2008 | 23.2°C | 17.1°C | 11.0°C | 30.9°C | 3.3°C | 72 mm | 74% | 0.2 m/s | 4 |
| 2007 | 24.1°C | 17.6°C | 11.2°C | 32.9°C | 3.4°C | 99 mm | 72% | 0.2 m/s | 4.5 |
| 2006 | 19.2°C | 14.5°C | 9.7°C | 24.8°C | 2.2°C | 99 mm | 83% | 0.2 m/s | 3.3 |
| 2005 | 24.7°C | 18.1°C | 11.6°C | 30.9°C | 4.6°C | 59 mm | 68% | 0.2 m/s | 4.7 |
| 2004 | 22.1°C | 16.9°C | 11.7°C | 26.9°C | 4.3°C | 144 mm | 83% | 0.2 m/s | 4.3 |
| 2003 | 21.2°C | 16.1°C | 11.0°C | 27.4°C | 4.0°C | 138 mm | 80% | 0.2 m/s | 3.9 |
| 2002 | 25.0°C | 18.6°C | 12.1°C | 33.8°C | 4.7°C | 124 mm | 66% | 0.2 m/s | 4.4 |
| 2001 | 22.1°C | 15.9°C | 9.7°C | 30.8°C | 2.7°C | 111 mm | 68% | 0.2 m/s | 4.4 |
| 2000 | 21.8°C | 15.5°C | 9.2°C | 30.7°C | -2.5°C | 77 mm | 70% | 0.2 m/s | 3.9 |
| 1999 | 23.5°C | 17.5°C | 11.4°C | 33.6°C | 4.3°C | 167 mm | 72% | 0.2 m/s | 4 |
| 1998 | 23.4°C | 17.1°C | 10.7°C | 31.1°C | 3.1°C | 67 mm | 72% | 0.2 m/s | 4 |
| 1997 | 20.8°C | 15.0°C | 9.2°C | 28.4°C | 2.0°C | 85 mm | 72% | 0.2 m/s | 3.8 |
| 1996 | 21.2°C | 16.2°C | 11.2°C | 29.4°C | 3.6°C | 127 mm | 79% | 0.2 m/s | 3.4 |
| 1995 | 21.5°C | 14.8°C | 8.1°C | 28.2°C | 0.2°C | 71 mm | 67% | 0.2 m/s | 4 |
| 1994 | 19.8°C | 14.6°C | 9.4°C | 26.6°C | 5.0°C | 75 mm | 80% | 0.2 m/s | 4 |
| 1993 | 20.3°C | 14.8°C | 9.2°C | 29.0°C | -0.1°C | 104 mm | 77% | 0.2 m/s | 3.2 |
| 1992 | 20.7°C | 14.9°C | 9.1°C | 27.7°C | -0.8°C | 110 mm | 77% | 0.2 m/s | 3.9 |
| 1991 | 21.6°C | 15.1°C | 8.6°C | 31.5°C | -2.7°C | 87 mm | 66% | 0.2 m/s | 4.1 |
| 1990 | 21.2°C | 15.4°C | 9.6°C | 29.4°C | 1.2°C | 85 mm | 74% | 0.2 m/s | 3.6 |
| 1989 | 22.1°C | 16.3°C | 10.4°C | 31.5°C | -0.1°C | 128 mm | 74% | 0.2 m/s | 3.7 |
| 1988 | 21.2°C | 14.9°C | 8.6°C | 27.6°C | 1.3°C | 55 mm | 71% | 0.2 m/s | 4.2 |
| 1987 | 20.3°C | 15.3°C | 10.3°C | 25.9°C | 3.0°C | 128 mm | 82% | 0.2 m/s | 3.4 |
| 1986 | 21.2°C | 15.4°C | 9.6°C | 28.6°C | 2.7°C | 86 mm | 76% | 0.2 m/s | 3.5 |
| 1985 | 23.1°C | 16.9°C | 10.6°C | 29.9°C | 3.1°C | 119 mm | 72% | 0.2 m/s | 4.2 |
| 1984 ❄️ | 20.0°C | 14.0°C | 8.0°C | 26.1°C | 2.4°C | 69 mm | 76% | 0.2 m/s | 4.2 |
| 1983 | 24.1°C | 17.2°C | 10.2°C | 31.8°C | 3.0°C | 51 mm | 62% | 0.2 m/s | — |
| 1982 | 22.9°C | 16.4°C | 9.8°C | 30.2°C | 3.3°C | 69 mm | 68% | 0.2 m/s | — |
| 1981 | 19.5°C | 14.6°C | 9.6°C | 26.6°C | 0.7°C | 134 mm | 79% | 0.1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 22.2°C with lows near 10.5°C (mean 16.4°C), based on 45 years of NASA POWER data.
September averages 98 mm of rainfall in Ithaca, a relatively wet time of year. The wettest on record was 248 mm in 2011.
The hottest September reached 33.8°C in 2002. The coldest dipped to -2.7°C in 1991.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.3°C. Daytime highs moved from 21.9°C to 22.7°C and overnight lows from 9.6°C to 11.4°C over the same span.
September is one of the warmer months of the year in Ithaca and a relatively wet time of year, so plan for around 22.2°C daytime highs and 10.5°C at night.
Not quite — September is the 9th coolest month in Ithaca, averaging 16.4°C.
For September in Ithaca, pack light layers you can adjust through the day, with typical highs of 22.2°C and lows of 10.5°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 74% — moderately humid.
Average wind speed in September is 0.2 m/s. The windiest September on record averaged 0.2 m/s (1982).
The wettest September on record was 2011 with 248 mm. On average, September sees 98 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 Ithaca 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.
