The Great Sand Dunes are located in the high elevation desert of the San Luis Valley at about , just west of the Sangre de Cristo Range. The dunefield's Köppen climate classification type is cold semi-arid (BSk), while the mountainous preserve's climate type is warm-summer humid continental (Dfb), at an average elevation of . Summer high temperatures are moderate with an average high temperature slightly above in July, which is the warmest month. The park's large spread between high and low temperatures, about , is typical of a high desert climate. Low temperatures during winter nights can be extremely cold, with average low temperatures well below and record low temperatures below from November through April. Precipitation is very low on the dunes, averaging just of rainfall per year. A high evaporation rate on the dunes qualifies the area as a desert, even though precipitation exceeds .