I have read about the heat this summer in southern Europe, and I haven't made any arrangements yet, but would it be too late to try to go to Switzerland, Murren and Lauterbrunnen by the end of July? If so, are there any suggestions for a last minute trip to northern Europe?
Of course it is not too late if you can buy plane tickets and reserve hotel rooms. You won't know until you try.
Booking.com is one good place to look for lodgings. When time is short and you are traveling during peak season, you probably don't want to waste time hitting thhe websites of individual hotels, most of which are probably sold out.
Edited to add: Check cancellation policies carefully. They vary by hotel, and some hotels offer both flexible and non-refundable options.