Is your trip solely around the Valley of Flowers? The trek closes down in October. If you're planning North India in December, its a better idea to go to the offbeat places which might have snow, and (Read More) you'll have a quiet, relaxing holiday. I would suggest Auli, Almora, Binsar in Uttarakhand for a 5 day trip. It might snow, and you'll have a great time.
No sagar , valley of flower mostly open in 1st of July. Sometimes in last week of May. . Because at end of the may snow start melting. If you are planning to go to valley of flower you should go in (Read More)month of June. Because at this time you can definitely find snow in some places..