About half of Arizona is semiarid, one-third is arid, and the remainder is humid. The Basin and Range region has the arid and semiarid subtropical climate that attracts most winter visitors and new residents. January days in Phoenix receive more than four-fifths of the possible sunshine and have a mean maximum temperature of 65 °F (18 °C).
Occasional light frosts occur at most locations in the Basin and Range region in winter, and some precipitation interrupts the exceedingly dry springs and mildly dry falls. Daily maximum readings average 106 °F (41 °C) in Phoenix in July, and nighttime temperatures drop to an average of 81 °F (27 °C).