In May, book hotels in advance?

jung,

Although May is "shoulder season", I've found that it can also be quite busy at that time of year. All of the places you listed are larger centres, so should have lots of accommodations available. However, one benefit of pre-booking is that you'll get to choose not only the price range and comfort level, but also which part of each town you want to stay. Pre-booking also means you won't have to waste time wandering about an unfamiliar city looking for a place to stay.

A couple of issues I encountered in England a few years ago....

• I arrived at a hotel in North Yorkshire expecting to get a room at the price shown on the internet. They informed me that price was only for pre-booked rooms, and the price for "walk-ins" was considerably higher. In my jet lagged state I decided to get the room, but I made sure that I got my money's worth at the breakfast buffet the next morning.
• I arrived at another hotel and asked about getting a room, and was informed that they only accepted pre-booking. I went out to the car, rang up the toll free number on my cell phone and got a booking, walked back inside the lobby with the reservation number and got my key.

I don't know if things on the continent are done the same way, as I always pre-book these days.

Thank you for your response. You are right. Yes, it makes sense to book in-advance. I just hope the weather cooperates on those days when we go up to the mountains, especially when we visit Zermatt :) Thanks!

No one, even the locals, will know what the weather is going to be in those mountains, which is especially unpredictable.
People usually make those decisions, on whether to go up high for a view, the day of.
Swiss hotels are so expensive that you'll want to book in advance to get a lower rate than the "walk in" rate.

Thank you, Kent.