Are most hotels air conditioned? If not, will sleeping be uncomfortable the end of August.
Where, specifically, in Switzerland? In the mountains, not a problem. At lower elevations, might be a wee bit warm.
Welcome to RS forum. If air conditioning is important to you, email each hotel to which you are interested to verify that all rooms are air conditioned assuming that info isn't made available on each hotel's website.
I don't know if this applies to Switzerland, but in many European countries, air-conditioning is not the same level of cold as in the U.S.
In general, the safest assumption is that air conditioning is NOT provided unless the hotel explicitly specifies that it is. (At least, this is the case in the two- to three-star hotels I stay in. Higher-end places may have different standards.)
Whether this makes sleeping uncomfortable depends on what you're used to. I was in Switzerland in late June, and none of the hotels I stayed in had air conditioning. In the mountains, this was no problem at all. In the cities, I kept the windows open and used a fan if one was provided. That kept the room at a comfortable temperature, although street noise was sometimes a problem. But I knew what I was getting into, and that I could have paid more to stay in plusher places if I'd wanted to. (Also, this was during the height of the World Cup, and there was a lot of celebratory shouting and horn-honking every night at 10:00 PM, whether Switzerland was playing that night or not.)
AC in Europe is not the norm. Don't assume your hotel has it - always verify. We knew our hotel in Geneva in June had no AC and we just happened to be there at the hottest day of the year so far. Fans helped a bit, but it was still hot and humid. 2 days later it turned cold, and I had to have a jacket with me. AC will cost you.
Air Conditioning was not needed in the mountains when we were there in July a few years ago. It was definitely needed in Zurich and we were quite happy to have it available.
Many European hotels that don't have air conditioning will have portable fans available upon request.
We were in Basel at the end of August of 2017. It was unseasonably hot. I believe it was over 90. Many were floating down the Rhine. We were happy our hotel had air conditioning. I usually double check as air conditioning is not a given in Europe and it would seem especially not in Switzerland.
The more modern hotels would have AC but be sure to verify. We are in Switzerland now and AC is essential in cities like Lucerne, Bern, Lausanne. Murren/Jungfrau region not so much.
We were in Zurich the second week of May this year. I chose Hotel Bristol even though it had no A.C. as I didn't think we'd need it. BIG mistake! We were on the 4th floor. The whole building was too warm. There was a table fan that was in the room, but it was woefully inadequate. We tried opening the windows, but that left us open to the street noises all night! I didn't get much sleep in this hotel. Yes yes, error on the side of comfort in case it is hot!