This week Wednesday, Phoenix reported a high temperature of 90 F. This is the earliest that Phoenix has ever reported a 90 F reading. The average date is March 30, and the previous record was February 24, set in 1904 and 1986. This may be due in part to the continuing dry conditions in the Southwest.
You can read more about it at https://ktar.com/story/911734/historic-heat-phoenix-reaches-earliest-90-degree-day-on-record/.
EarthSky also pointed out that the Southwest is becoming drier due to changes in weather patterns which control the flow of moisture through the region. You can read their discussion here.
