September is one of the warmer months of the year in Mcallen, with average highs near 33.6°C and lows around 23.6°C (mean 28.6°C). It is a relatively wet time of year, averaging 113 mm of rainfall and 71% relative humidity across the period.
September is one of the warmer months of the year in Mcallen. Across 45 years of records, the warmest September in Mcallen was 2023 — when the month averaged 32.5°C — while the coldest was 2008 at 26.4°C. Typical September days reach 33.6°C with nights near 23.6°C. The long-term trend is warming, about 0.4°C per decade.
September is a relatively wet time of year in Mcallen, averaging 113 mm of rainfall. The wettest September on record was 2003 with 263 mm, while the driest was 2023 at 18 mm.
Relative humidity in Mcallen during September averages 71%. The most humid September was 2003 at 81%, and the least humid was 2011 at 58%.
September receives about 5.4 kWh/m²/day of solar energy in Mcallen. The sunniest September was 2023 at 6.4 kWh/m²/day, and the cloudiest was 1984 at 4.6.
Average wind speed in Mcallen during September is 2.8 m/s. The windiest September was 1986 at 3.7 m/s, while the calmest were 2007 and 2022 at 2.1 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 28.2°C | 28.2°C | 28.2°C | 29.2°C | 29.5°C | +1.3°C |
| Avg High | 33.3°C | 33.1°C | 33.0°C | 34.1°C | 34.7°C | +1.4°C |
| Avg Low | 23.1°C | 23.3°C | 23.4°C | 24.2°C | 24.3°C | +1.2°C |
| Avg Rain | 89 mm | 108 mm | 148 mm | 114 mm | 100 mm | +11 mm |
September temperatures in Mcallen have risen by about 1.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 13.4°C (2020) to a record high of 42.1°C (2000).
Rainfall in September is a relatively wet time of year, averaging 113 mm, with a wettest year of 263 mm.
A quieter season to visit Mcallen
If your dates are flexible, the more temperate months of March and November tend to be the most comfortable for visiting Mcallen. That said, September — with days averaging 33.6°C and nights around 23.6°C (mean 28.6°C) and higher rainfall (113 mm) — can still be rewarding for travellers who don't mind the warmth, and often means fewer crowds.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 34.7°C | 29.7°C | 24.7°C | 39.4°C | 21.0°C | 88 mm | 70% | 2.3 m/s | 5.6 |
| 2024 | 33.2°C | 28.7°C | 24.3°C | 35.3°C | 20.0°C | 216 mm | 78% | 2.4 m/s | 5.2 |
| 2023 🔥 | 38.9°C | 32.5°C | 26.1°C | 40.8°C | 24.1°C | 18 mm | 60% | 2.9 m/s | 6.4 |
| 2022 | 33.9°C | 28.8°C | 23.7°C | 36.3°C | 18.1°C | 96 mm | 70% | 2.1 m/s | 5.5 |
| 2021 | 34.4°C | 29.2°C | 24.1°C | 37.5°C | 18.3°C | 69 mm | 70% | 2.7 m/s | 5.9 |
| 2020 | 33.1°C | 28.0°C | 23.0°C | 38.1°C | 13.4°C | 114 mm | 72% | 3 m/s | 5.2 |
| 2019 | 34.2°C | 29.7°C | 25.2°C | 37.6°C | 23.5°C | 102 mm | 72% | 3.1 m/s | 5.5 |
| 2018 | 32.9°C | 28.7°C | 24.5°C | 38.5°C | 21.4°C | 159 mm | 77% | 2.5 m/s | 5 |
| 2017 | 34.8°C | 29.5°C | 24.1°C | 37.4°C | 19.4°C | 66 mm | 67% | 3.2 m/s | 5.4 |
| 2016 | 35.5°C | 30.2°C | 25.0°C | 38.7°C | 21.4°C | 68 mm | 67% | 2.9 m/s | 5.7 |
| 2015 | 33.9°C | 28.9°C | 23.8°C | 37.6°C | 19.9°C | 118 mm | 73% | 2.7 m/s | 5.7 |
| 2014 | 32.0°C | 28.0°C | 24.1°C | 37.2°C | 21.0°C | 222 mm | 79% | 2.7 m/s | 4.9 |
| 2013 | 32.0°C | 27.9°C | 23.7°C | 38.0°C | 18.6°C | 209 mm | 77% | 2.6 m/s | 4.9 |
| 2012 | 36.0°C | 30.0°C | 23.9°C | 40.3°C | 20.9°C | 30 mm | 62% | 3.3 m/s | 5.9 |
| 2011 | 37.1°C | 30.6°C | 24.1°C | 39.5°C | 19.5°C | 23 mm | 58% | 2.9 m/s | 6.3 |
| 2010 | 32.3°C | 28.0°C | 23.7°C | 36.1°C | 15.3°C | 147 mm | 77% | 2.5 m/s | 5.2 |
| 2009 | 33.5°C | 28.6°C | 23.7°C | 38.9°C | 16.7°C | 148 mm | 71% | 2.5 m/s | 4.9 |
| 2008 ❄️ | 31.0°C | 26.4°C | 21.7°C | 36.4°C | 16.6°C | 145 mm | 77% | 2.2 m/s | 5.3 |
| 2007 | 32.0°C | 27.8°C | 23.6°C | 34.9°C | 20.9°C | 92 mm | 80% | 2.1 m/s | 5.5 |
| 2006 | 32.9°C | 28.3°C | 23.6°C | 38.3°C | 17.9°C | 249 mm | 74% | 2.8 m/s | 5.3 |
| 2005 | 35.4°C | 30.1°C | 24.9°C | 40.6°C | 22.5°C | 52 mm | 68% | 2.7 m/s | 5.7 |
| 2004 | 33.2°C | 28.5°C | 23.7°C | 37.0°C | 21.1°C | 134 mm | 72% | 2.3 m/s | 5.2 |
| 2003 🌧️ | 31.2°C | 27.4°C | 23.7°C | 35.0°C | 19.7°C | 263 mm | 81% | 2.4 m/s | 4.7 |
| 2002 | 32.9°C | 27.9°C | 22.9°C | 37.4°C | 17.3°C | 195 mm | 73% | 2.7 m/s | 5.3 |
| 2001 | 32.5°C | 27.6°C | 22.8°C | 38.2°C | 16.4°C | 151 mm | 74% | 2.9 m/s | 5.7 |
| 2000 | 35.3°C | 29.2°C | 23.1°C | 42.1°C | 15.4°C | 47 mm | 61% | 3.1 m/s | 5.9 |
| 1999 | 33.5°C | 28.1°C | 22.7°C | 37.8°C | 17.0°C | 104 mm | 69% | 2.8 m/s | 5.7 |
| 1998 | 32.8°C | 28.6°C | 24.3°C | 38.4°C | 22.4°C | 203 mm | 77% | 2.6 m/s | 4.8 |
| 1997 | 34.5°C | 29.1°C | 23.7°C | 38.1°C | 18.9°C | 82 mm | 68% | 2.5 m/s | 5.7 |
| 1996 | 33.5°C | 28.6°C | 23.7°C | 38.4°C | 15.0°C | 70 mm | 73% | 3 m/s | 5.8 |
| 1995 | 33.3°C | 28.3°C | 23.2°C | 36.6°C | 14.8°C | 99 mm | 72% | 2.4 m/s | 5.7 |
| 1994 | 33.9°C | 28.2°C | 22.5°C | 37.8°C | 17.4°C | 59 mm | 65% | 2.5 m/s | 5.4 |
| 1993 | 32.0°C | 27.5°C | 22.9°C | 37.3°C | 15.8°C | 170 mm | 76% | 2.7 m/s | 5.5 |
| 1992 | 33.9°C | 28.7°C | 23.5°C | 38.9°C | 16.5°C | 61 mm | 68% | 3.3 m/s | 5.4 |
| 1991 | 31.2°C | 26.9°C | 22.6°C | 35.1°C | 14.6°C | 124 mm | 75% | 2.5 m/s | 5 |
| 1990 | 32.8°C | 28.1°C | 23.5°C | 36.1°C | 19.2°C | 106 mm | 71% | 2.5 m/s | 5.3 |
| 1989 | 33.9°C | 28.0°C | 22.1°C | 37.2°C | 14.4°C | 48 mm | 62% | 2.9 m/s | 6 |
| 1988 | 32.7°C | 27.7°C | 22.7°C | 35.0°C | 18.8°C | 152 mm | 74% | 3.3 m/s | 5.3 |
| 1987 | 34.0°C | 28.6°C | 23.1°C | 38.2°C | 18.0°C | 92 mm | 68% | 3 m/s | 5.5 |
| 1986 | 34.2°C | 29.5°C | 24.7°C | 36.3°C | 23.4°C | 72 mm | 70% | 3.7 m/s | 5.5 |
| 1985 | 33.9°C | 28.8°C | 23.7°C | 37.4°C | 14.9°C | 64 mm | 69% | 3.2 m/s | 5.7 |
| 1984 | 31.0°C | 26.5°C | 22.1°C | 35.3°C | 14.2°C | 173 mm | 75% | 3.3 m/s | 4.6 |
| 1983 | 32.3°C | 27.7°C | 23.2°C | 37.3°C | 15.6°C | 122 mm | 74% | 3 m/s | — |
| 1982 | 35.0°C | 29.3°C | 23.5°C | 39.0°C | 20.0°C | 36 mm | 64% | 2.9 m/s | — |
| 1981 | 32.7°C | 27.8°C | 22.9°C | 34.9°C | 15.9°C | 42 mm | 73% | 2.6 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 33.6°C with lows near 23.6°C (mean 28.6°C), based on 45 years of NASA POWER data.
September averages 113 mm of rainfall in Mcallen, a relatively wet time of year. The wettest on record was 263 mm in 2003.
The hottest September reached 42.1°C in 2000. The coldest dipped to 13.4°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.8°C. Daytime highs moved from 33°C to 35°C and overnight lows from 23.1°C to 24.6°C over the same span.
September is one of the warmer months of the year in Mcallen and a relatively wet time of year, so plan for around 33.6°C daytime highs and 23.6°C at night.
Not quite — September is the 8th coolest month in Mcallen, averaging 28.6°C.
For September in Mcallen, pack light, breathable clothing and sun protection, with typical highs of 33.6°C and lows of 23.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 71% — moderately humid.
Average wind speed in September is 2.8 m/s. The windiest September on record averaged 3.7 m/s (1986).
The wettest September on record was 2003 with 263 mm. On average, September sees 113 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 Mcallen 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.
