An intense and unseasonably early heatwave swept across the southwestern United States this week, setting multiple temperature records and culminating in what appears to be the highest March temperature ever recorded in the country.
According to the National Weather Service, a temperature of 110°F (43.3°C) was measured near Martinez Lake, a small settlement in the Yuma Desert along the Arizona–California border. This surpasses the previous national March record of 108°F (42.2°C), originally set in 1954 in Rio Grande City.
The earlier record had already been matched a day prior in North Shore, signaling the widespread and escalating nature of the heat event. By Thursday, additional locations across California—including Cathedral City and Thermal—also recorded temperatures of 108°F, coinciding with the final day of winter.
Forecasts indicated that Thermal could reach 110°F by Friday, potentially equaling the newly established record. The weather service noted that such temperatures are highly atypical for this time of year, pointing out that the first occurrence of 105°F conditions in the region generally does not happen until late May.
The heatwave has affected a broad swath of the Southwest, with record highs reported in major metropolitan areas including Phoenix, San Diego, Los Angeles, Las Vegas, and San Francisco.
In Phoenix, temperatures climbed to 105°F (40.6°C) on Thursday, exceeding the previous day’s record of 102°F (38.9°C). The city also experienced its earliest instance of triple-digit heat on record, with such conditions not having occurred in March for nearly four decades. Authorities responded by closing local hiking trails due to elevated risks of heat-related illness.
Las Vegas similarly broke records, reaching 95°F (35°C), slightly above the prior high set just one day earlier.
Despite the extreme conditions, some residents continued routine activities. In Thermal, a local worker reported taking precautions such as staying hydrated while working outdoors, reflecting a degree of acclimatization to desert climates.
Meteorologists indicate that temperatures across the region are expected to remain significantly above seasonal norms—by as much as 20 to 30 degrees Fahrenheit—through the end of the week. A modest cooling trend is anticipated, though conditions are still likely to remain warmer than average. Additionally, several cities may experience their earliest recorded instances of temperatures exceeding 100°F in the coming days.
