Hello!
I’m planning my vacation for next year and I can’t decide between Sept or Oct. I want do do maybe one to two day hikes in each of the counties I’ll be visiting. Which do you think is the best month to visit Switzerland, Austria and Slovenia? I’ll have 24 days in total. I’m also considering June but I have read that there will still be snow in Switzerland in the mountains. I was in Italy and France last June and I had an amazing weather in Chamonix and Val Gardena but it was uncomfortably hot in the cities. This is the reason I’m thinking between Sept and Oct. Visiting these countries during fall when the color of leaves are changing will be a dream but is it true it will be constantly raining?

Looking forward to your recommendations.
Thanks in advance.

sept for sure for Switzerland and Austria hiking. October in Swiss higher climes/climbs could see ice and snow on trails.

You can get climate statistics -- including rainfall -- in just about any decent guidebook or at timeanddate.com.

Hope that helps!

September for hiking in Slovenia, too. October is fine for lower altitude day hikes, but there will be more rain. This year has been a bit of an outlier with a poor September and a great October, it's almost always the other way around.

September it is then. I was leaning towards this month anyway. Thank you all for the replies.

There is no significant difference in climate between Chamonix and the Swiss Alps.
October is usually drier than September in the Swiss Alps; this year there was almost no rainfall during the whole month. I walked in the Canton of Valais at altitudes of 2000-2600 metres just a few days ago and it was really dry (and rather warm at the sun). The contrast between blue sky and the red resp. yellow coloured leafs and needles of trees and other plants was beautiful!
But snowfall cannot be completely excluded after mid September.
In Switzerland, many mountain railways (not the famous one's of course)and bus lines over alpine passes stop to run in mid October.
I would plan to begin in Slovenia and to end in Switzerland before mid/end October.

And the earlier in September the better.

Thank you neckervd for this suggestion. You’ve been a great help to me while I was planning my Italy and France vacation last year. It was my first time in Europe and I was travelling solo and I am very thankful to all the replies you and other commenters gave to my questions. My 3-week trip was a success!

Correction to my comment above: my France and Italy trip was this year in June not last year.