Sils Maria / St. Moritz to San Candido/Innchen Italy

I cannot comment on driving, but I can on the weather (July versus September). Basically, it can be anything in the mountains. We have been in Switzerland, the Dolomites, and most recently the Julian Alps in the months of June, July, August, and September, and have experienced a mix of weather from warm and sunny to cold and rainy/snowy in each month.

We were in Slovenia this past September and experienced the weather you observed with your weather watch. We hiked in snow in The Julian Alps, and read of associated flooding in Croatia, as well as Tuscany. So the bad weather was widespread. And we were told it was somewhat unusual.

By contrast, the previous September (2016) we were in the Engadine (Samedan, close to St. Moritz) for two days at the end of September, and had one glorious day of sunshine, followed by a cloudy but dry day.

in 2015 we had half-sunny, half-drizzly weather for our one week hiking trip in the Dolomites in late September. No snow, though. In earlier Dolomite trips we were twice driven indoors by thunderstorms (late August). We have hiked in a blizzard in early July in Switzerland (Zermatt) and enjoyed sunshine the day after.

As for crowds, September is less crowded than July in the mountain areas. Kids go back to school in late August, at least in Italy, so families are not on vacation in September. We found that hotel prices in the Dolomites can drop significantly around Sept. 1.

Thanks. so good weather is basically pure luck :)