Arizona’s climate is arid and semi-arid, with average annual precipitation ranging from 3 inches in the southwest at Yuma to around 40 inches in the White Mountains in east central Arizona.The southwestern desert is hot, with winter daytime temperatures in the lower 60s and summer daytime temperatures between 105 and 115 F.Nighttime temperatures on the desert drop slightly below freezing in the winter, while elsewhere in the state, winter nights frequently drop into the 20s.