Mexicali broke two heat records in 48 hours this week, reaching 42.7°C (108.9°F) on Wednesday, March 19, just one day after setting a previous March high of 42.2°C (108°F) on Tuesday. Both readings are part of a broader extreme heat event that Yale Climate Connections called “one of the most extreme weather events in world history” for the Southwest U.S. and northwest Mexico.
March 19 Temperature Beat 2017 Record by Over 5 Degrees
Wednesday’s 42.7°C reading did not just edge past the day before. It obliterated the previous record for March 19, which stood at 37.5°C (99.5°F), set in 2017. That is a margin of more than 5 degrees Celsius, an extraordinary jump for a single calendar date.
Mexicali, the capital of Baja California, sits in the Sonoran Desert just south of Calexico, California. The city regularly records Mexico’s highest summer temperatures. In August 2025, Mexicali hit 52.7°C (126.9°F). But those extremes typically arrive in June, July, or August, not in the third week of March.
City Officials Activated Emergency Protocols Early
Mexicali city officials began fast-tracking emergency heat relief measures on March 18, months ahead of schedule. The Imperial Valley Press reported that the city triggered its extreme heat playbook before midweek, with cooling centers and hydration stations opening earlier than any previous year. Health authorities warned residents about heat stroke and dehydration, especially for outdoor workers and the elderly.
The heat was not confined to Mexicali. On Thursday, Hermosillo, Sonora, recorded 42.5°C (108.5°F), setting a new national March record for Mexico. Across the border, Phoenix hit 105°F on March 19, smashing its all-time March record of 100°F from 1988. Flagstaff, Arizona, beat its March record by 11 degrees.
What Drove the Extreme Temperatures
Yale Climate Connections reported that this March heat wave would have been “virtually impossible” without climate change. The analysis noted that March now shows the most substantial long-term warming trend for heat extremes across the affected region. Temperatures were expected to climb even higher on Friday and Saturday in some areas.
Mexicali’s two consecutive records also raise concerns about electricity demand. The city’s grid faces heavy strain during peak cooling months, and an early start to extreme heat could test CFE (Mexico’s federal electric utility) capacity well before summer. Residents who cross regularly to Calexico or the Imperial Valley should expect similar conditions on both sides of the border, as reported by The Baja Post.