Letterkenny Weather in September
Average highs run from 16°C on September 1 to 14°C on September 30, and lows from 11°C to 9°C. Normal precipitation for the month is 99 mm over about 18 wet days.
September day by day
The normal high and low for each date, in °C.
- Normal low
- Normal high
- Reanalysis extreme high
- Reanalysis extreme low
September at a glance
- Average high
- 15°C
- Average low
- 10°C
- Precipitation
- 99 mm
- Reanalysis high
- 22°CSep 1, 1991
- Reanalysis low
- 5°CSep 27, 2010
- Daylight
- 13 h 46 min to 11 h 38 min
- Cloud cover
- 79%
- Humidity
- 88%
- Dew point
- 10°C
- Wind
- 21.2 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 | Reanalysis high | Reanalysis low | Chance wet |
|---|---|---|---|---|---|
| Sep 1 | 16°C | 11°C | 22°C 1991 | 9°C 1994 | 66% |
| Sep 2 | 16°C | 11°C | 20°C 1991 | 9°C 2008 | 65% |
| Sep 3 | 16°C | 11°C | 20°C 1991 | 7°C 2018 | 65% |
| Sep 4 | 16°C | 11°C | 21°C 1991 | 7°C 1992 | 66% |
| Sep 5 | 16°C | 11°C | 21°C 1999 | 6°C 1992 | 66% |
| Sep 6 | 16°C | 11°C | 19°C 2016 | 6°C 2013 | 67% |
| Sep 7 | 16°C | 11°C | 19°C 2016 | 8°C 2018 | 66% |
| Sep 8 | 16°C | 11°C | 20°C 2020 | 8°C 2006 | 67% |
| Sep 9 | 15°C | 11°C | 19°C 2004 | 8°C 2013 | 66% |
| Sep 10 | 15°C | 10°C | 18°C 2006 | 9°C 2014 | 65% |
| Sep 11 | 15°C | 10°C | 20°C 2000 | 8°C 1991 | 65% |
| Sep 12 | 15°C | 10°C | 19°C 2006 | 6°C 1999 | 64% |
| Sep 13 | 15°C | 10°C | 20°C 2003 | 7°C 1992 | 63% |
| Sep 14 | 15°C | 10°C | 19°C 2020 | 7°C 1993 | 63% |
| Sep 15 | 15°C | 10°C | 19°C 2020 | 7°C 2015 | 62% |
| Sep 16 | 15°C | 10°C | 19°C 2020 | 6°C 2015 | 63% |
| Sep 17 | 15°C | 10°C | 19°C 2003 | 6°C 1993 | 62% |
| Sep 18 | 15°C | 10°C | 17°C 2020 | 6°C 2017 | 62% |
| Sep 19 | 15°C | 10°C | 19°C 2019 | 7°C 1997 | 60% |
| Sep 20 | 15°C | 10°C | 20°C 1998 | 7°C 2009 | 59% |
| Sep 21 | 15°C | 10°C | 20°C 1998 | 6°C 2012 | 59% |
| Sep 22 | 15°C | 9°C | 19°C 2013 | 6°C 2012 | 60% |
| Sep 23 | 14°C | 9°C | 20°C 2013 | 6°C 1992 | 60% |
| Sep 24 | 14°C | 9°C | 18°C 2019 | 6°C 2018 | 61% |
| Sep 25 | 14°C | 9°C | 17°C 2019 | 7°C 2018 | 62% |
| Sep 26 | 14°C | 9°C | 18°C 2018 | 6°C 2010 | 63% |
| Sep 27 | 14°C | 9°C | 18°C 2013 | 5°C 2010 | 64% |
| Sep 28 | 14°C | 9°C | 20°C 2011 | 5°C 2018 | 64% |
| Sep 29 | 14°C | 9°C | 18°C 2011 | 6°C 2018 | 66% |
| Sep 30 | 14°C | 9°C | 18°C 2014 | 5°C 1991 | 67% |
Chance of rain
- Chance of a wet day
Sunrise and sunset
Times for 2026, local time (GMT+1).
- September 1
- sunrise 6:37 AM, sunset 8:23 PM
- September 30
- sunrise 7:31 AM, sunset 7:09 PM
Other months
Sources
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 2026-09-25. Sun and moon: computed with the NOAA solar equations and Meeus.