The temperatures in Letterkenny in September are quite cold with temperatures between 8°C and 16°C, warm clothes are a must.
You can expect about 3 to 8 days of rain in Letterkenny during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Letterkenny in September 2025.
If you’re planning to visit Letterkenny in the near future, we highly recommend that you review the 14 day weather forecast for Letterkenny before you arrive.
Temperatures
16° / 8°
Rainy Days
6
Snowy Days
0
Dry Days
24
Rainfall
59
mm
Sun Hours
2.2
Hrs
