Summary (tl;dr)

Southern California is under its earliest-ever "extreme heat watch" as a historic heatwave is forecast to bring record-breaking temperatures 20-30 degrees above normal to the region next week, raising significant health concerns.

Essential Background

Globally, the past few years have seen a consistent trend of rising temperatures, with 2023, 2024, and 2025 ranking among the hottest years on record, and 2026 projected to continue this pattern. This warming trend has been linked to an increased frequency and intensity of heatwaves and other extreme weather events worldwide. The National Weather Service (NWS) updated its terminology last year, changing "excessive heat watch" to "extreme heat watch" to reflect the severity of these events.

The Full Story

Currently, an unprecedented and historic heatwave is gripping Southern California and other parts of the U.S. Southwest, prompting the National Weather Service to issue its first-ever "extreme heat watch" for the Los Angeles area in March. This watch, in effect from Monday morning through Friday evening, covers a wide arc of Southern California, including communities from the Central Coast to inland areas like Santa Clarita, Riverside, and San Bernardino. Temperatures are forecast to be 20 to 30 degrees above normal for this time of year, with many inland communities expected to reach into the 90s, and some areas potentially exceeding 100 degrees Fahrenheit. This long-duration heat event is so unusual for March that it is expected to break daily and monthly temperature records, and potentially challenge all-time March records in some locations. Other cities in the Southwest, such as Phoenix and Death Valley, are also anticipating triple-digit temperatures that could break historical March records.

Why It Matters

This early-season extreme heat poses a significant risk of heat-related illnesses, especially for vulnerable populations such as the elderly, young children, and individuals without air conditioning. The intensity and unusual timing of this heatwave highlight the escalating impacts of climate change, which scientists say is increasing the frequency and severity of such extreme events. Public health officials and meteorologists are urging residents to take precautions, stay hydrated, seek cooling centers, and check on neighbors to prevent heat-related emergencies. The forecast is described as "extraordinary for March" and could be one of the top heat wave events for the month ever recorded, signaling a concerning shift in weather patterns.

Geographic Location

• Los Angeles County, California, United States (earliest-ever extreme heat watch issued, record-breaking temperatures expected, including Los Angeles, Santa Clarita, and other inland communities)
• Ventura County, California, United States (extreme heat watch issued, record-breaking temperatures expected, including Ventura County Beaches, Central Ventura County Valleys, and Malibu Coast)
• San Diego County, California, United States (extreme heat watch issued, including Santa Ana Mountains and Foothills)
• San Bernardino County, California, United States (extreme heat watch issued, record-breaking temperatures expected)
• Riverside County, California, United States (extreme heat watch issued, record-breaking temperatures expected)
• San Luis Obispo County, California, United States (extreme heat watch issued for Central Coast)
• Santa Barbara County, California, United States (extreme heat watch issued for Central Coast)
• Phoenix, Maricopa County, Arizona, United States (forecasted to reach 100+ degrees, challenging earliest 100-degree record)
• Death Valley, Inyo County, California, United States (forecasted to reach 108 degrees, challenging earliest 100-degree and 105-degree records)
• Las Vegas, Clark County, Nevada, United States (predicted to reach 100 degrees)