Air conditioning necessary in August?

I would definitely get AC in cities like Bern and Lucerne. Windows don't have screens so opening them lets in bugs, cigarette smoke and noise and maybe a breeze. Closing the windows to keep out the annoyances also keeps out any chance of a breeze to cool the room.

You are probably finding so few hotels have A/C for a few reasons - Europeans tend to be much more energy conscious than North Americans with A/C a huge power drain and retrofitting historic buildings would be challenging and expensive ... but mostly because the temperature generally doesn't get hot enough (high temps in August are around the 24 degree C point) to justify it. Personally, I wouldn't choose a hotel simply because it has A/C to drown out street noise and I'm a light sleeper. If you are that concerned about street noise look for a quieter neighbourhood or ask for a room off the street or at the end of a hall. You can also get white noise apps for smartphones and tablets ... or even pack a pair of ear plugs. With the temperatures generally being so moderate, I'd choose location over a hotel with A/C.

Good luck finding what you are looking for and have a great trip!

You're had some good advice above. I see that Rick's hotel listings address some noise issues and places where you could request quieter rooms, and at least one in Bern is listed in a quieter residential area. Even without AC, the hotel may be able to provide a fan. My other tips: stay out late with all the noisy people; and take cold showers to keep cool.

North of the Mediterranean basin, there's generally less than two weeks or less of the summer where US-style air conditioning is needed. Some summers, not at all. That being said, you're more likely to miss it in cities than in the mountains.