Several commenters said they apply the same general principle to trap cool air in a room. Commenter cindy54536 prefers a blanket for a thicker blocker, and Cindy and nikki8112 both say that blankets can also keep warm air in in the wintertime.
Juneau, with its cold climate and coastal location, has humidity levels heightened by temperatures that rarely exceed 65°F, receiving over 250 days of precipitation annually.