We have always travelled to Europe in the Spring or Fall to try to avoid crowds (or at least relative crowds). We are looking at RS best of Germany/Austria/Switzerland, and the summer months are all that are available for 2024. What are others experience visiting during the summer months, pros and cons?
Summer travel: often hot and humid in Germany, less so in Switzerland, and crowded in those destinations that appear in the GAS tour. The only summer advantage I see is that certain attractions are open slightly longer than in the other seasons.
It would be my choice to continue your spring/fall habit when you visit Germany. As long as your visit takes place between Easter and November 1, you can count on things being open pretty much everywhere. Fall festivals are numerous. The weather and the tourist crowds are less stressful. These countries are some of the most accessible in Europe to the foreign visitor doing independent travel... English is widely spoken, train transport is highly developed, personal safety/security levels are very high... you probably don't need a tour. And of course, one person's "best of" isn't another's... For me, the best of Germany would start with Berlin, the Rhine Valley, the German Alps, and Franconia, in no particular order - but these areas are not allocated any serious time at all on the GAS tour. Doing your own tour over 2 weeks in spring or fall would be pretty simple.
We lived in Augsburg, Germany from 87-91 and loved the German Summers. I am from South Georgia and German Summers don't compare much to those in Georgia.
It can get hot in Germany, but extreme heat is not common. The higher you go in elevation, the cooler it gets.
By the way, Switzerland is amazing, but cost usually run about 50% higher than Austria or Germany.
Pro: The beer gardens are open. Lots of outdoor concerts and events.
Con: Crowds in the most popular tourist spots, museums, etc.
It may be a bit hot in Germany, but not so bad as to cause one to not take the trip. Austria and Switzerland will be cooler. One advantage is that there are more daylight hours during which to do things. We did that tour several years ago and really enjoyed it. Definitely go over at least a day early in case there are transportation problems.