Scotland/Ireland trip - September or May?

May - because the days are getting longer.

Thank you ! That is a great reason to go in May!

I'm sure both places are beautiful in September too, but the long days in May make it easier to see lots of sights before it gets dark. And many spring flowers are in bloom. Be aware, though, that temperatures will probably be chilly.

I went there in late October. The days were short. I was glad I packed a rain jacket and an extra sweater.

I'd go in May if it were me, and if not then, I'd pick early September between your choices.

We were in Scotland in early September two years ago and the weather was beautiful--the best they'd had all summer according to our B&B host. And on our two trips to Ireland, both in September, the weather was also quite good--a scattering of rainy days but mostly sunny or partly cloudy and warm enough to get by in sweatshirts or light jackets. We didn't really notice the days getting shorter until the very end of the month. Clearly the other folks who have responded had nice weather in May too so I'd recommend choosing whichever time frame is cheaper and/or more convenient for you. As an aside--we loved the golf courses in Dingle and Westport. We had both of them mostly to ourselves on weekdays in September and the weather was lovely.

Thank you all!

I don't know about Scotland but I've been to Ireland four times and always early October (most recently two years ago). Weather has always been great.

We were in Scotland in May and Ireland in October. Both were two week trips and either May or September/October are both nice times of year to visit. You won’t be disappointed with either choice.