What is the best time to visit Dalhousie and its surrounding areas in Himachal Pradesh?

I would say the best time to visit Dalhousie and its surrounding areas in Himachal Pradesh would be:

Best Time In Winters: November – March

Best Time In Summers: April to September

Above is the best time to visit Dahousie and Himachal Pradesh, also if you plan for Dalhousie during Winters (December – March) which is the ideal time for snowfall, you might get a chance to experience live snowfall as well.