Marion is a census-designated place and unincorporated community in Flathead County, Montana, United States. Its population was 886 as of the 2010 census. Marion has a post office with ZIP code 59925.This climatic region is typified by large seasonal temperature differences, with warm to hot summers and cold winters. According to the K�ppen Climate Classification system, Marion has a humid continental climate, abbreviated "Dfb" on climate maps.