Sure you can get a little moisture brought into your attic space from wind/rain/moist air but attic rain is typically cause by warm and MOIST air from your house leaking into the cold attic space. When its minus fucking 45 for weeks straight that warm MOIST air leaking into your attic condenses and freezes on your trusses and on the u/s of your roof sheathing. It then slowly builds up over multiple days/weeks to create a whole shit ton of ice build up. Like this:
Then the chinook rolls in and it melts super quickly, drips down onto your attic insulation, finds its way down to your ceiling vapour barrier then travels to any holes (staples, light fixture, bath fans, etc) and stains your ceiling. The more ice you had the more water you’ll get when it melts
The real fix is having a continuous ceiling vapour barrier so warm MOIST air doesn’t leak into the attic. Then you don’t get the ice build up and big melt off when a chinook rolls in.
You can also add more ventilation (vented soffits, roof vent, power vents, etc) to move more air out of the attic quicker when the big melts happen but that not really fixing the core issue.