It's great that you're thinking of visiting County Donegal
this September! Like many places, some parts of Donegal will be busier during the holiday period. Don't worry though, you will be able to enjoy the rugged wilderness even during peak season, as there is more than enough to explore. :)
What would you like to see and do while you're here? Donegal is the most northern county along the Wild Atlantic Way,
and you can follow the road all the way up to (my personal favourite spot) Malin Head
. You'll find loads of walking and hiking
trails, both along the coast and more inland. If you have the time, make sure not to miss out on Glenveagh National Park
. It's really peaceful and absolutely gorgeous.
If you're planning on spending most of your time outdoors, September is a great time of year to visit Donegal. The weather
is usually nice and mild, and on average it's warmer than in August. The temperatures averages between 12 and 18 degrees, with some chance of rain.
Hope this helps, and let me know if you have any other questions!