 It is mostly constructed of Marston Mat and was built by the United States Navy Seabees.Despite being located at 28°12'N which is north of the Tropic of Cancer, Midway Atoll has a tropical savanna climate (Köppen "Aw") with very pleasant year-round temperatures.Rainfall is evenly distributed throughout the year, with only two months being able to be classified as dry season months (May and June).