Arizona has a dry climate, with little rainfall. Temperatures vary greatly from place to place, season to season, and day to night. Average daily temperatures at Yuma, in the southwestern desert range from 43° to 67°F (6° to 19°C) in January, and from 81° to 106°F (27° to 41°C) in July. At Flagstaff, in the interior uplands, average daily January temperatures range from 14° to 41°F (–10° to 5°C), and average daily July temperatures range from 50° to 81°F (10° to 27°C). The maximum recorded temperature was 128°F (53°C), registered at Lake Havasu City on 29 June 1994; the minimum, –40°F (–40°C), was set at Hawley Lake on 7 January 1971.

The highest elevations of the state, running diagonally from the southeast to the northwest, receive between 25 and 30 in (63 to 76 cm) of precipitation a year, and the rest, for the most part, between 7 and 20 in (18 to 51 cm). Average annual precipitation at Phoenix (1971–2000) was 8.3 in (21 cm). The driest area is the extreme southwest, which receives less than 3 in (8 cm) a year. Snow, sometimes as much as 100 in (254 cm), falls on the highest peaks each winter but is rare in the southern and western lowlands.

The greatest amount of sunshine is registered in the southwest, with the proportion decreasing progressively toward the northeast; overall, the state receives more than 80% of possible sunshine, among the highest in the US, and Phoenix's 86% is higher than that of any other major US city.