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Early heatwave grips southwestern US
An unusually intense heatwave is sweeping across the southwestern United States this week, bringing summer-like temperatures to the region far earlier than normal. Phoenix, Arizona, could see temperatures top 100°F (38°C) as early as Wednesday-the earliest triple-digit heat in nearly 40 years, according to the National Weather Service (NWS).
Heat dome fuels extreme temperatures
A slow-moving high-pressure system, commonly referred to as a heat dome, is trapping hot air over California, Nevada, and Arizona, pushing temperatures 20-30°F above seasonal averages. The heat is expected to persist for days, with minimal overnight cooling exacerbating the risk for residents.
Forecasts indicate widespread highs above 90°F, including in typically cooler coastal areas, while inland and desert regions may exceed 110°F, threatening long-standing March records.
Health and environmental risks mount
The NWS has issued heat advisories for parts of California, including the Bay Area and central coast, where temperatures could reach 90°F. Authorities are urging residents to check on vulnerable populations, such as the elderly, and to avoid outdoor activities during peak heat.
"Extreme early-season heat, combined with high tourism rates, will make this event particularly dangerous for those unaccustomed to such conditions," the Las Vegas NWS office warned.
The heatwave also threatens California's already below-average snowpack, accelerating melt at a time when it typically builds or declines gradually. Rapid runoff could reduce water supplies later in the year, as snowpack provides roughly a third of the state's water.
Wildfire concerns shift across regions
While the heatwave alone isn't expected to trigger large wildfires in the Southwest-due to lighter winds-conditions are far riskier further east. From the Rockies to the High Plains, dry air, parched vegetation, and persistent breezes could create ideal conditions for fires to ignite and spread rapidly.
Heatwave follows extreme weather elsewhere
The southwestern heatwave contrasts sharply with recent weather in other parts of the country, including blizzards in the Midwest and Great Lakes, as well as severe thunderstorms and tornado threats along the East Coast. By late week, above-average temperatures are expected to expand across much of the United States.
Outlook
Forecasters predict only gradual relief by the weekend or early next week, raising concerns about prolonged health risks and broader environmental impacts, including an extended wildfire season.
