| ºF | Earliest | Latest | 1978-2007
Average |
| 90 | 24-Feb | 12-May | 31-Mar |
| 91 | 24-Feb | 16-May | 2-Apr |
| 92 | 25-Feb | 16-May | 4-Apr |
| 93 | 5-Mar | 24-May | 6-Apr |
| 94 | 9-Mar | 24-May | 11-Apr |
| 95 | 10-Mar | 27-May | 15-Apr |
| 96 | 16-Mar | 1-Jun | 16-Apr |
| 97 | 16-Mar | 1-Jun | 20-Apr |
| 98 | 16-Mar | 13-Jun | 24-Apr |
| 99 | 16-Mar | 13-Jun | 28-Apr |
| 100 | 26-Mar | 18-Jun | 1-May |
| 101 | 6-Apr | 18-Jun | 9-May |
| 102 | 6-Apr | 19-Jun | 13-May |
| 103 | 7-Apr | 23-Jun | 17-May |
| 104 | 7-Apr | 23-Jun | 19-May |
| 105 | 20-Apr | 13-Jul | 23-May |
| 106 | 2-May | 13-Jul | 29-May |
| 107 | 2-May | 13-Jul | 31-May |
| 108 | 3-May | 9-Aug | 4-Jun |
| 109 | 3-May | 9-Aug | 6-Jun |
| 110 | 8-May | 9-Aug | 10-Jun |
Based on the long-term data record (1896-2007), the first 90° F day occurs in Phoenix, on average, by April 4th. However, that date has been slowly moving up in the year - most likely due to the increasing urbanization of the region. Based on the last 25 years, the average date is April 1st, and the last 10 years yields a date of March 29th. The earliest 90 °F day occurred on February 24th in 1904 and again in 1986. The latest was May 12th in 1912.
Based on the long-term data record (1878-2007), the first 90° F day occurs in Yuma, on average, by March 22nd. The earliest 90° F day occurred on February 3rd in 1963. The latest was May 3rd in 1975.
The selection of 90º F is fairly subjective. Why not focus on 93° F or 101° F? The graph to the right shifts the focus away from a single number, instead detailing the higher range of temperatures routinely observed in Phoenix. The individual data can be found in the table to your right.
