Educational film explaining how weather works continues with an explanation of the other major air masses. Shot of map of North America with white circle for Polar Canadian air mass with another white circle for Polar Pacific air mass appearing. Shot of Pacific coastline. Shot of snow on "high Western mountains" [?] Another shot of map with addition of Polar Atlantic air mass. Shot of foggy highway. Shot of trees in heavy snow. Return to map with the addition of Tropical Continental, Tropical Gulf, and Tropical Atlantic at the bottom of the map. Shots of palm trees, tropical landscape. CU shot of newspaper article with headline: "98 Sets Heat Record Here." Return to map with addition of Tropical Pacific air mass. Shot of Pacific coastline/ beach. Shot of snow-covered "mountains near the West Coast" [Sierra Nevadas?]