A late-season heat event is holding across a wide stretch of the country, and forecasters have put Extreme Heat Warnings in place from the Arizona deserts to northwest Arkansas. The western warnings run through Thursday evening in most areas and through Friday evening in the Imperial Valley, which means the exposure is measured in days rather than hours.
The specific numbers explain why the alerts carry the strongest heat label the National Weather Service uses. In the Colorado River Valley and Death Valley, forecasters projected high temperatures of 112 to 116 degrees, with 105 to 110 in the Las Vegas Valley, Moapa Valley and Pahrump Valley. In Imperial County and the Imperial Valley, afternoon temperatures of 106 to 112 were expected. The Phoenix metropolitan area was forecast to reach 105 to 109, and the Yuma area 107 to 110. Across northwest and west central Arkansas and eastern Oklahoma, the NWS Tulsa office warned of heat index values above 110.
That combination matters most for households that cannot easily escape it. The warnings cover daytime windows on consecutive days, and forecasters in Phoenix noted that cloud cover is limiting overnight cooling, leaving morning lows well above normal and offering little relief between afternoons. That cumulative load is what turns an uncomfortable stretch of weather into an emergency visit for an older adult, an outdoor worker, or a person whose air conditioning has failed.
Where the Alerts Are Posted and What They Mean
An Extreme Heat Warning is issued when dangerous heat is happening or about to happen, and the National Weather Service tells the public that a warning means take action rather than prepare. A Heat Advisory covers dangerous conditions falling short of warning criteria.
The current western warnings cover portions of northwest Arizona, southeast California and southern Nevada, including Death Valley National Park, Lake Havasu, Lake Mead and Lake Mohave, along with the Phoenix metro area, the Yuma area and Imperial County. In the southern Plains, the Tulsa forecast office has issued back-to-back one-day warnings for parts of northwest and west central Arkansas and eastern Oklahoma, including Tulsa, Muskogee and Sebastian County.
Heat Advisories reached farther, covering additional parts of Arkansas and Oklahoma as well as California's San Joaquin Valley, the Sierra Nevada foothills, and the Riverside and San Diego County mountains.
Thresholds differ by region. Local offices set criteria based on what residents are acclimated to, so a September number that would be routine in July can meet warning criteria now.
Cramps, Exhaustion and the Point Where Heat Becomes an Emergency
Heat illness moves along a progression rather than arriving all at once. Heat cramps are painful muscle spasms, often in the legs or abdomen, that follow heavy sweating. Heat exhaustion brings heavy sweating, cold and clammy skin, a fast but weak pulse, nausea, dizziness, headache, and muscle weakness. It generally responds to moving somewhere cool, loosening clothing, sipping water, and applying cool cloths.
Heatstroke is different. Body temperature climbs to 103 degrees or higher, skin may become hot and dry or damp, the pulse becomes fast and strong, and the person may become confused, lose consciousness, or stop making sense. Heatstroke is a medical emergency that requires calling 911 and moving the person to a cooler place while waiting. People with suspected heatstroke should not be given anything to drink.
Confusion is the warning sign most often missed at home. A relative who becomes irritable, disoriented or unusually sleepy during a heat event is not merely tired, and that change alone warrants urgent evaluation.
Federal figures show the annual scale. A CDC fact sheet states that in an average year, heat causes 67,512 emergency department visits, 9,235 hospitalizations and 702 deaths in the United States. CDC surveillance published in the agency's Morbidity and Mortality Weekly Report analyzed heat-related visits to 826 emergency departments and found that more males than females sought care, and that the federal region covering Arkansas, Louisiana, New Mexico, Oklahoma and Texas had the highest visit rate in the country.
Groups Carrying the Heaviest Burden During a September Event
Risk is not spread evenly. Older adults, infants and young children, pregnant people, and people with heart, lung or kidney disease face the greatest danger of severe outcomes. So do people taking certain medications, including some diuretics, antipsychotics, stimulants and drugs with anticholinergic effects, which can blunt sweating or fluid balance. Nobody should stop a prescribed medication because of a forecast, but a pharmacist can advise on timing and warning signs.
Outdoor workers in construction, agriculture, delivery, and roofing carry a distinct occupational risk during the hottest hours of the day. The Occupational Safety and Health Administration recommends frequent rest breaks in shaded or air-conditioned spaces, guidance the Weather Service repeats in the text of the current warnings. Athletes and marching band students returning to fall practice also appear regularly in late-season heat illness data, because training often resumes before acclimatization is complete.
Housing conditions shape risk as much as biology. Residents of older buildings without central air, upper-floor units, and households behind on utility bills face longer indoor exposure. The CDC's heat and health surveillance work tracks emergency department visits for heat-related illness in near real time by region, which local health departments use to spot surges early.
Cooling Centers, Utility Protections and Free Local Options
Most metro areas in the alert zone operate cooling centers during declared heat events, typically at libraries, community centers and senior centers. County emergency management or 211 lines can identify the nearest one, and many are free.
Households worried about disconnection should ask their utility about shutoff moratoriums, medical certificates and payment plans. Several states restrict disconnection during declared heat emergencies or when a household member has a documented medical need for cooling. The federal Low Income Home Energy Assistance Program helps with cooling costs in many states, through state or county offices.
Practical steps carry more weight than any single number on a forecast. Reschedule strenuous activity to early morning or evening, drink water before feeling thirsty, and check on older neighbors and relatives at least once a day during a multi-day warning. Never leave a child or pet in a parked car, where interiors reach lethal temperatures within minutes. Fans alone do not protect people once indoor air rises above about 90 degrees, because moving hot air over skin can add heat rather than remove it.
Forecasters expect some relief east of the Rockies late in the week, while heat persists across the southern Plains. Warnings are reissued daily, so residents should check the current alert for their county.
Key Questions Answered
Which areas are under an Extreme Heat Warning? Warnings cover portions of northwest Arizona, southeast California and southern Nevada, plus the Phoenix metro area, the Yuma area, Imperial County, and parts of northwest and west central Arkansas and eastern Oklahoma. The Imperial Valley warning runs latest, into Friday evening.
How hot is it expected to get? Forecasters projected 112 to 116 degrees in Death Valley and the Colorado River Valley, 105 to 110 in the Las Vegas Valley, 106 to 112 in the Imperial Valley and 105 to 109 in metro Phoenix. Heat index values above 110 were expected in parts of Arkansas and Oklahoma.
What is the difference between a warning and an advisory? A warning means dangerous heat is occurring or imminent, and residents should take action. An advisory covers dangerous conditions that do not reach warning criteria. Thresholds vary by local weather office.
When does heat illness become an emergency? Call 911 for a body temperature of 103 degrees or higher, confusion, loss of consciousness, hot skin, or a fast and strong pulse. Do not give anything to drink to someone with suspected heatstroke.
Who faces the highest risk? Older adults, infants and young children, pregnant people, people with heart, lung, or kidney disease, outdoor workers, athletes, and people taking medications that affect sweating or fluid balance.
Where can people cool off if they lack air conditioning? County emergency management offices and 211 lines can identify local cooling centers, often at libraries, community centers, and senior centers. Many operate free of charge during declared heat events.
Can a utility shut off power during a heat warning? Rules vary by state. Households should ask their utility about heat-related moratoriums, medical certificates, and payment plans, and can check eligibility for federal energy assistance through state or county offices.
