A record-breaking heat wave has gripped the Southwest, with a temperature of 110°F recorded near Martinez Lake, Arizona, marking a new high for March in the U.S. The extreme heat, affecting Arizona, California, and Nevada, has pushed temperatures 20 to 40 degrees above average. Phoenix shattered its previous March record, reaching 105°F. The National Weather Service attributes this to a persistent high-pressure system creating a heat dome. Over 18 million people are under extreme heat warnings, prompting advisories to stay hydrated, seek air-conditioned environments, and limit outdoor activities, especially for vulnerable groups like the elderly and children.