Hi karthik you can visit anywhere in uttarakhand or himachal in north india during mid june .Staying anywhere else will be really sweltering .I guess you can go to nainital,bhimtal or bhowali (if you want a quieter place) Simla will be really crowded so places close to simla or manali but not exactly in the heart of those places will be really good you can enjoy the hills and the weather without getting in the rut of traffic of the main places.in a nutshell any quieter place in the hills will do the trick for you .HAVE FUN