San Juan Weather in September
Average highs run from 24°C on September 1 to 24°C on September 30, and lows from 18°C to 18°C. Normal precipitation for the month is 207 mm over about 27 wet days.
September day by day
The normal high and low for each date, and the record, in °C.
- Normal low
- Normal high
- Record high
- Record low
September at a glance
- Average high
- 24°C
- Average low
- 18°C
- Precipitation
- 207 mm
- Record high
- 36°CSep 14, 1979
- Record low
- 14°CSep 16, 1977
- Daylight
- 12 h 18 min to 12 h 02 min
- Cloud cover
- 80%
- Humidity
- 91%
- Dew point
- 19°C
- Wind
- 2.9 km/h
Every day of the month
A wet day has at least 1 mm of precipitation in the reanalysis.
| Date | Normal high | Normal low | Record high | Record low | Chance wet |
|---|---|---|---|---|---|
| Sep 1 | 24°C | 18°C | 31°C 1976 | 16°C 2020 | 85% |
| Sep 2 | 24°C | 18°C | 31°C 2010 | 16°C 2007 | 84% |
| Sep 3 | 24°C | 18°C | 31°C 2003 | 16°C 1980 | 84% |
| Sep 4 | 24°C | 18°C | 35°C 1977 | 16°C 1999 | 84% |
| Sep 5 | 24°C | 18°C | 33°C 1978 | 16°C 1984 | 84% |
| Sep 6 | 24°C | 18°C | 31°C 1997 | 16°C 1977 | 85% |
| Sep 7 | 24°C | 18°C | 32°C 1976 | 15°C 1977 | 85% |
| Sep 8 | 24°C | 18°C | 30°C 2008 | 16°C 1979 | 86% |
| Sep 9 | 24°C | 18°C | 31°C 2015 | 17°C 1985 | 87% |
| Sep 10 | 24°C | 18°C | 32°C 2009 | 16°C 1978 | 86% |
| Sep 11 | 24°C | 18°C | 31°C 2024 | 16°C 1978 | 86% |
| Sep 12 | 24°C | 18°C | 34°C 1983 | 15°C 1981 | 87% |
| Sep 13 | 24°C | 18°C | 31°C 2023 | 16°C 1977 | 87% |
| Sep 14 | 24°C | 18°C | 36°C 1979 | 16°C 1977 | 87% |
| Sep 15 | 24°C | 18°C | 31°C 2023 | 16°C 1978 | 87% |
| Sep 16 | 24°C | 18°C | 31°C 2023 | 14°C 1977 | 88% |
| Sep 17 | 24°C | 18°C | 32°C 1979 | 15°C 1977 | 90% |
| Sep 18 | 24°C | 18°C | 31°C 2001 | 15°C 1977 | 90% |
| Sep 19 | 24°C | 18°C | 31°C 2016 | 15°C 1977 | 90% |
| Sep 20 | 24°C | 18°C | 31°C 1981 | 16°C 1977 | 90% |
| Sep 21 | 24°C | 18°C | 31°C 2009 | 15°C 1977 | 90% |
| Sep 22 | 24°C | 18°C | 31°C 2015 | 16°C 1977 | 90% |
| Sep 23 | 24°C | 18°C | 31°C 2015 | 15°C 1977 | 90% |
| Sep 24 | 24°C | 18°C | 31°C 2023 | 16°C 1977 | 91% |
| Sep 25 | 24°C | 18°C | 31°C 2013 | 15°C 1985 | 92% |
| Sep 26 | 24°C | 18°C | 29°C 2006 | 15°C 1985 | 92% |
| Sep 27 | 24°C | 18°C | 33°C 1983 | 15°C 1985 | 92% |
| Sep 28 | 24°C | 18°C | 32°C 2015 | 15°C 1985 | 92% |
| Sep 29 | 24°C | 18°C | 30°C 2023 | 15°C 2022 | 92% |
| Sep 30 | 24°C | 18°C | 31°C 2009 | 16°C 1980 | 90% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (CST).
- September 1
- sunrise 5:27 AM, sunset 5:45 PM
- September 30
- sunrise 5:25 AM, sunset 5:27 PM
Other months
Sources
Records: NOAA GHCN-Daily, station CSM00078762, every year on file, quality-flagged values removed. Cloud, humidity, wind and sunshine, and temperature and precipitation: NASA POWER (MERRA-2, CERES and GEWEX SRB), 1991-2020. The data was obtained from the National Aeronautics and Space Administration (NASA) Langley Research Center's Prediction Of Worldwide Energy Resources (POWER) project funded through the NASA Earth Science Division: POWER Daily API v2, accessed 2026-09-24. Sun and moon: computed with the NOAA solar equations and Meeus.