Is 6 flags open in December?

Yes.. it's open on weekends, (except Christmas Eve which falls on a Sunday this year) & the week following Christmas for their Holiday in the Park themed celebrations.

Only weekends and select Friday's for holiday in the park

Yes, it is open on some select dates in December

Yes, its Christmas themed

Yes it is. They have Holiday in the Park from Thanksgiving to Christmas

Yes, holiday in the park was a lot of fun!

Depends which six flags, but most say december 6 the park is closed

Yes

Yes, they have transformed the park into a Holiday Winterfest. Beautiful.