State and local weather officials have escalated heat alerts as a strong dome of high pressure moves over Arizona, setting the stage for an intense stretch of summer temperatures across the Valley and beyond. An Extreme Heat Warning takes effect Tuesday, and First Alert Weather Days have been declared for Tuesday, Wednesday and Thursday as daytime highs are expected to climb well into the triple digits.
Loading post…
Phoenix temperatures graphic showing a forecast high of 114°F Tuesday and a 90°F Tuesday night, illustrating the extreme-heat outlook prompting expanded heat warnings.
Forecast guidance issued ahead of the heat surge places expected high temperatures across the Valley in a roughly 111- to 116-degree range over the coming days. Meteorologists describe the pattern as a robust ridge of high pressure building overhead, the atmospheric configuration responsible for suppressing cloud cover and allowing temperatures to spike into the mid-110s.
Regional forecast map with a dominant high-pressure 'H' over Arizona, the weather pattern driving First Alert Weather days and the expanded heat warning across the state.
Official forecasts indicate Phoenix will see some of the highest readings, with one graphic showing a forecast high of 114°F for Tuesday and lingering warmth into the overnight hours — a projected low of about 90°F Tuesday night. The extended outlook points to the hottest day of the year so far coming in the middle of the week, with several forecasts calling for highs near or around 115 degrees by midweek.
The warning and alert designations are in place for the core of the workweek: Tuesday through Thursday. Those First Alert Weather Days correspond with the strongest period of the heat ridge, when daytime heating is expected to peak and night-time temperatures will remain elevated. Forecast messaging released alongside the watches underscores that the hottest conditions are expected during that three-day window.
The heat pattern is broad enough that warnings and advisories have been expanded beyond the immediate Phoenix metro area to encompass other parts of the state. Forecast materials circulated with the announcements show the same dominant high-pressure signature over Arizona that will be responsible for the prolonged stretch of very hot conditions.
Evening conditions are expected to offer little relief in some locations. Forecast detail highlighted in the distributed graphics projects overnight temperatures remaining near 90 degrees for parts of the Valley on Tuesday night, a level that can limit cooling and prolong heat exposure from one day to the next. That sustained warmth through the overnight period is noted in the same briefs that identify the three-day advisory window.
Public communications tied to the current forecast emphasize the timing and intensity of the event. The alerts take effect Tuesday, with the most intense heat expected through Thursday as the ridge holds. Forecast updates circulated by local weather operations in recent days show the pattern building into place and sustaining itself long enough to produce multiple consecutive days of peak summer heat across large portions of Arizona.
The National Weather Service Phoenix office has confirmed the Extreme Heat Warning also covers portions of southeast California, where afternoon temperatures of 109 to 117°F are expected along with major HeatRisk. Local outlets including KOLD have additionally noted increasing storm chances later in the week once the high-pressure ridge begins to shift.
The National Weather Service in Phoenix said the Extreme Heat Warning is in effect from 10 a.m. Tuesday to 8 p.m. MST Thursday for lower desert zones in Arizona, and from 10 a.m. Tuesday to 8 p.m. PDT Thursday for parts of southeast California.
NWS forecasters named the lower deserts — including the Phoenix metro, Yuma and El Centro — among the areas covered and noted they upgraded an earlier Extreme Heat Watch to an Extreme Heat Warning as confidence in the event increased.
In its forecast discussion NWS projected overnight lows in the urban core to average in the mid‑80s and reach as warm as the low‑90s, and said HeatRisk values are expected to range from moderate to major across much of the region during the Tuesday–Thursday period.
Forecasters also warned the warning could be extended into Friday if the subtropical ridge shifts more slowly or farther west than currently expected.