Phoenix’s early-season heat eases this week as highs slip below 100°F after record March spike

A record-setting March warm spell begins to weaken across metro Phoenix

Phoenix is expected to step down from triple-digit highs this week as the weather pattern that drove an unusually intense March heat episode starts to shift. After several days of record-level warmth, forecast temperatures are trending lower heading into the weekend and early next week, though conditions are still expected to run warmer than typical for late March.

The heat surge pushed Phoenix into rare territory for the month. The city reached triple-digit readings unusually early in the season, and daytime highs climbed well above long-standing daily benchmarks. In mid-March, Phoenix hit 101°F on a Wednesday, marking the earliest triple-digit temperature recorded for the city. The following day, Phoenix reached 105°F, exceeding the previous day’s record and establishing another notable March milestone for the metro area.

Why temperatures are falling: a changing upper-level pattern

The warm spell has been associated with strong high pressure over the Southwest, a setup that suppresses cloud formation, enhances sunshine, and favors rapid daytime heating. Forecast guidance indicates that high pressure influence will gradually weaken and shift east late in the week, allowing a more unsettled pattern to develop over parts of the western United States. For central Arizona, that change is expected to bring a downward trend in high temperatures, taking Phoenix out of the triple digits.

Alongside the cooling trend, a modest increase in atmospheric moisture is possible as winds turn more favorable for a northward push of humidity. While widespread rainfall is not guaranteed, forecast probabilities include low-end chances for showers—focused mainly over higher terrain east of Phoenix—beginning around Sunday. Any precipitation would be spotty and highly dependent on the timing and strength of the pattern shift.

Public impacts: heat precautions remain relevant even below 100°F

Even as the peak heat relaxes, elevated temperatures for this time of year can still pose health risks, especially for people without reliable cooling, those working outdoors, and individuals sensitive to heat. Heat-related illness risk can rise quickly during prolonged outdoor activity, particularly in very dry air when dehydration can occur faster than expected.

• Outdoor plans may become more manageable as highs ease, but hot afternoons remain likely.
• Hydration and limiting strenuous activity during peak heat hours remain important.
• Conditions can vary across the Valley, with the warmest readings typically in lower-elevation urban areas.

Regional context: a broader Southwest heat event

Phoenix’s heat arrived as part of a larger warm spell across the Southwest that produced record-breaking temperatures in multiple states. The broader episode included exceptionally high March readings in desert locations near the Arizona–California border, highlighting the scale of the warm air mass affecting the region.

Phoenix is moving away from the most extreme portion of the March heat, but temperatures are expected to remain above seasonal norms as the transition unfolds.

Forecast conditions will be refined day by day as the pattern shift approaches, but the overall direction is clear: Phoenix is set to drop out of triple digits this week, ending a brief, historically unusual stretch of mid-March heat.