Phoenix Issues First Alert Days for Heavy Rain and Storms From Tropical Moisture

Tropical moisture streaming northward from Hurricane Polo is set to collide with an incoming Pacific weather system, bringing a distinct threat of scattered thunderstorms, heavy rain, and localized flooding to the Valley this week according to local forecasts. First Alert Days have been officially issued for Monday and Tuesday as meteorologists track the atmospheric intersection.

Tracking the Remnants of Hurricane Polo Toward Arizona

While the core of Hurricane Polo will remain safely offshore of Mexico, its massive atmospheric plume is pulling north. Forecasters note that the system is merging with an incoming storm system arriving from the northwest. This dynamic is ramping up rain chances across the Valley to 50% on Monday and hitting 60% by Monday night into Tuesday.

Before the heavy moisture arrives, residents can expect mostly cloudy skies on Sunday with daytime highs reaching the upper 90s, alongside a slight chance of light evening and overnight showers. The approaching storm front will then knock temperatures down significantly, dropping highs to near 90 on Monday and into the upper 80s on Tuesday before dry, near-century heat returns by next weekend.

Flood Watches Expand Across Northern and Southern Arizona

Although the Phoenix metropolitan area is not currently under an active Flood Watch, neighboring regions are preparing for severe impacts. Flood watches are scheduled to take effect Sunday night across northern and eastern Arizona, followed by southern Arizona on Monday morning.

Photo: signalsaz.com

The broader regional outlook highlights high forecast uncertainty earlier in the week, heavily tied to Polo’s precise trajectory off the coast of Mexico.

Preparing for the Valley’s Shift to Wet Weather