That trip was 2007 and yes, I believe that climate change has altered weather patterns since then.
We did not return to Switzerland until 2018, with our son and his family (twin grandchildren). We went in early August, arriving in the middle of a heatwave all over that part of Europe. It did not bother us too much at the elevation of Muerren, but on our way there we experienced a lot of heat in Amsterdam, and Freiburg. The heatwave ended 2 days after we left Muerren for Chamonix to start hiking the Tour du Mont Blanc (our son’s family went home). The earth’s fever broke with a boom—-literally. A huge thunderstorm with torrents of rain that caused mudslides and rockfall in the Alps, including one the Tour du Mont Blanc trail we were due to hike 2 days later. Fortunately we were with a guided group, and our guides were able to work out a shuttle transfer past the blocked point on the trail.
We did not see many wildflowers on that August trip; even in the little alpine botanical garden above Muerren most of the flowers were spent and dry. It may have been because of the heatwave. Or maybe even in a more normal year the cows have grazed them out of all the meadows. But I did see, in two separate places, a flower I had never seen before or even heard of, the mahogany-red Gentiana purpurea.
https://www.inaturalist.org/taxa/349697-Gentiana-purpurea
The first few were along the North Face trail above Muerren, in an area that fences out the cows. We saw many more, a field full of them, in a meadow we traversed on a high trail on the Tour du Mont Blanc in Italy. This must have been cow-free meadow, as it was very lush and green.
This is now my favorite wildflower, and I wanted to make our next trip to Switzerland in early August to see them again. I knew My son and his family, especially the twins, were hoping to return to Switzerland, so I proposed the trip for August 2023. My daughter-in-law said they would love to go, but not in August, due to heat and crowds. She suggested late September, which meant taking the twins out of school for 2 weeks, but that was fine. For the 2 weeks we were in Switzerland (Muerren again, and Weggis near Luzern) and the Dolomites, we had one day with intermittent rain. The rest of the time the weather was perfect. But we saw no wildflowers at all.
The past few summers, at least, it seems Europe has been hit with either extreme heat, or excessive rains and flooding, or both.