At Jay Peak, to close the upper lifts winds have to go over 65-70 mph. And yes, I have ridden up when it felt really hairy and shortly after I got off, they closed it!
Different resorts have different max winds, based on type of chair, exposure, etc., but most resorts in VT don't close chairs till winds hit about that.
When it's really windy, stay in the shelter of the trees.
Bonni, you want to see winds over 50 mph, go to Jay, Whiteface or Tremblant.
: It's not "all the time," of course, but when the winds hit that hard, it's darn freaky. My husband has a good story about patrolling at Jay when the winds were more than 70 mph and nothing but the T-bars were open...