On March 20, 2026, the southwestern United States and parts of Mexico were hit by an unprecedented heatwave, marking an exceptionally hot start to spring. NASA's Earth Observatory reported record-breaking temperatures, with Yuma, Arizona, reaching 109°F (43°C), significantly above the normal climatological average. Other locations in Arizona and California, including Martinez Lake and Winterhaven, experienced temperatures as high as 112°F (44°C). The heatwave extended into Mexico, where Hermosillo set a new March record at 108°F (42°C). This extreme weather event was caused by a persistent high-pressure system, similar to those typically seen in summer, which kept the region dry and clear for over a week. The GEOS model indicated temperatures exceeding 104°F (40°C) across vast areas, underscoring the severity of the heat.