Oklahoma is located in a humid subtropical region. Oklahoma lies in a transition zone between humid continental climate to the north, semi-arid climate to the west, and humid subtropical climate in the central, south and eastern portions of the state. Most of the state lies in an area known as Tornado Alley characterized by frequent interaction between cold, dry air from Canada, warm to hot, dry air from Mexico and the Southwestern U.S., and warm, moist air from the Gulf of Mexico. The interactions between these three contrasting air currents produces severe weather (severe thunderstorms, damaging thunderstorm winds, large hail and tornadoes) with a frequency virtually unseen anywhere else on planet Earth. An average 62 tornadoes strike the state per year—one of the highest rates in the world.