Dangerous Heat Advisory Issued: How to Stay Safe Amid Record-Breaking Temperatures This Week

Millions under heat advisories as 2025’s first major heat wave stretches from Alaska to the Mojave The National Weather Service (NWS) has expanded heat advisories and excessive-heat warnings across more than a dozen states this week, marking the most widespread early-summer alert since 2021. Unseasonably strong high-pressure ridges are squeezing thermometers well above normal from the Arctic Circle to the Southwest desert, shattering local records and raising wildfire and health concerns. Southern California: Inland deserts flirt with 120°F • An advisory covering Orange County’s inland corridors, the Inland Empire and San Diego’s valleys now runs through at least Wednesday evening. Palm Springs could spike to 118°F, while Palmdale and San Bernardino are forecast to top 103°F and 101°F, respectively, before a modest cooldown late Thursday. • An extreme-heat warning blankets Death Valley National Park and the I-15 corridor to Las Vegas, where heat indices may exceed 115°F. Record warmth reaches the Last Frontier For the first time in recorded history, Alaska is using the same formal heat-alert system as the Lower 48. Advisories were issued when interior readings were projected to reach 85°F—levels that dramatically elevate heat-stroke risk for residents unaccustomed to such warmth. Fairbanks neighborhoods and parts of the North Slope climbed into the upper 80s Tuesday, while red-flag fire warnings remain in place because rapid snowmelt is drying tundra fuels. Why this heat wave is different Meteorologists attribute the early burst of extreme temperatures to a “double-ridge” pattern: 1. A heat dome anchored over the Desert Southwest is forcing hot, dry air toward California and Nevada. 2. A separate ridge parked over western Canada is funneling subtropical air unusually far north, raising temperatures and humidity from British Columbia into interior Alaska. Together, the twin ridges are stalling typical Pacific storm tracks, limiting cloud cover and allowing solar radiation to build for days. The result: daytime highs 15–25°F above average and overnight lows that provide little relief. Health impacts escalate quickly Heat-related illness can set in when the heat index exceeds 90°F. The NWS warns that dehydration, heat exhaustion and heat stroke are possible within 10–30 minutes for vulnerable populations, including outdoor workers, children and older adults. Emergency rooms in Riverside County reported a 27% uptick in heat complaints Monday compared with the previous week, according to the county health department. Wildfire risk rising Low humidity (5–15%) and gusty downslope winds are combining with parched grasses to create critical fire weather over the Grapevine, Antelope Valley foothills and the eastern Sierra. A fire-weather watch is posted from Alpine County, California, into western Nevada through Friday, with single-spark ignitions capable of rapid expansion on south-facing slopes. How to stay safe during a heat advisory Authorities recommend the following actions whenever an advisory is in effect: • Hydrate before you feel thirsty—two to four cups of water every hour if working outside. • Reschedule strenuous activity to early morning or after sunset. • Wear loose, light-colored clothing and a wide-brimmed hat; apply SPF 30+ sunscreen. • Never leave children, pets or electronics in a parked car, even for a few minutes. • Check on neighbors who are elderly, disabled or lack air-conditioning. • Know the signs of heat illness: heavy sweating, dizziness, confusion, rapid pulse. Call 911 if body temperature exceeds 103°F or the person becomes unconscious. Cooling resources • Los Angeles, San Diego and Clark counties have opened more than 60 cooling centers, libraries and mall lounges; locations are available by calling 211. • National parks including Joshua Tree and Death Valley advise visitors to finish hikes before 10 a.m., carry a gallon of water per person and remain within sight of shade or a vehicle. Outlook Model ensembles show the Southwestern ridge weakening by the weekend, trimming temperatures 5–10°F. However, the northern ridge may linger, keeping Alaska and western Canada unusually warm into next week. Climate scientists note that earlier, longer heat events are consistent with the long-term warming trend and urge residents to view this week’s advisories as a preview of what an “above-average” summer could bring.