Phoenix starts Sunday near 80 degrees, but the late-September heat is about to lose its grip. Temperatures will climb to nearly 98 degrees before rain chances increase Sunday night and a much cooler, stormier stretch arrives Monday and Tuesday.
Moisture is expected to increase Sunday, with possible light rain later in the day. The National Weather Service says isolated showers could begin Sunday evening, with a slight chance of thunderstorms overnight and temperatures holding near the upper 70s.
Storm Chances Increase Monday Night
Monday brings a noticeable cool-down, with partly sunny skies and a high near 87 degrees. Scattered showers and thunderstorms could develop mainly from late Monday afternoon onward, with the rain chance rising to 80% Monday night as temperatures fall to around 72.
Some parts of the lower desert could pick up between a half-inch and three-quarters of an inch of rain Monday night. Heavier totals are possible in higher terrain areas north and east of Phoenix, where localized flooding may become a concern.
Flood Watch Covers Parts Of Phoenix Area
A Flood Watch is set to take effect late Monday night and continue through Tuesday evening for foothill areas of northern Maricopa County, along with northern and eastern portions of the Phoenix metro and higher terrain farther east. Tuesday is expected to bring showers and thunderstorms, a high near 85 and a 70% chance of precipitation.
Residents should be prepared for ponding on roads, sudden visibility drops and fast-changing conditions during heavier downpours. Never drive through a flooded roadway, even if the water looks shallow, and keep outdoor plans flexible from Monday night through Tuesday.
Sunny Skies Return By Wednesday
The unsettled pattern should wind down Tuesday night, followed by a sunny Wednesday with a high near 89. Warmer weather returns gradually, with a high of 93 Saturday and Phoenix potentially reaching 100 by next weekend.
For Sunday, the best window for outdoor plans is before evening, though the combination of heat and increasing clouds will make it feel like the atmosphere is changing by the hour. The bigger weather story arrives after dark, when Phoenix shifts from summer heat to showers and thunderstorms.
