A dry line is a boundary that separates a moist air mass from a dry air mass. Also called a "Dew Point Front", sharp changes in dew point temperature can be observed across a dry line. Dry lines are most commonly found just east of the Rocky Mountains, separating a warm moist air mass to the east from a hot dry air mass to the west.

States like Texas, New Mexico, Oklahoma, Kansas, and Nebraska frequently experience dry lines in the spring and summer. Dry lines are extremely rare east of the Mississippi River.