A ridge of high pressure parked over the Western United States has put roughly 55 million people under heat alerts, with triple-digit temperatures stretching from Las Vegas north to the Canadian border and dozens of daily records already broken.
Las Vegas reached 115 degrees on Saturday, its hottest reading of the year and one degree short of the daily record, according to Associated Press reporting carried by NBC News. Phoenix was forecast to reach 116 and El Centro, California, 118.
The event is expected to be short-lived, which is the part most likely to be misread. Heat does not kill during the hottest hour. It kills over consecutive days in households where the indoor temperature never comes back down, and the federal record shows that population is larger than most people assume.
Records Falling Across a Dozen States
The list of broken records on Saturday alone ran from the desert to the northern Rockies. The Weather Channel documented new highs in Billings and Great Falls, Montana, at 104; Helena at 103; Pocatello, Idaho, at 103; Cedar City, Utah, at 100; Grand Junction, Colorado, at 104; and El Centro at 118. Riverton, Wyoming, broke its all-time August record at 100. Death Valley may approach 125 during the stretch.
Montana matters here in a way Phoenix does not. Air conditioning penetration is far lower in the northern Rockies than in the Southwest, and a 104-degree day in Billings lands on housing stock built for a different climate. Most of Montana was also under a red flag warning, with National Weather Service meteorologists telling the AP they were watching fire risk closely as high winds moved in.
In Nevada, an NWS meteorologist described afternoon humidity bottoming out in the single digits across much of the state, a condition that raises both fire danger and the rate at which a person outdoors loses fluid without noticing.
The National Weather Service issues an extreme heat warning for conditions that "pose a significant threat to life," a threshold distinct from the advisory level used for less severe discomfort. Both were in effect across the region this weekend.
The Federal Death Count and Its Known Blind Spot
The number most often repeated in heat coverage is out of date, and the correction runs in one direction.
CDC's own summary materials for its Heat and Health Tracker describe an average year in the United States as producing about 67,512 emergency department visits, 9,235 hospitalizations, and 702 deaths. Those averages draw on older baselines. Death-certificate data compiled through CDC's environmental health tracking program tell a steeper story: heat-related deaths recorded nationally rose from 1,069 in 1999 to 2,415 in 2023, the highest on record, with 2,394 recorded in 2024.
Even those figures are floors rather than ceilings. Heat frequently acts by aggravating an existing heart or kidney condition, and in those cases the death certificate often names the cardiac or renal event without naming the temperature that triggered it. CDC notes that hospital-based data may not capture the full range of heat-related illness when excess heat exposure is not explicitly documented.
Local counts fill some of the gap. In Maricopa County, home to Phoenix, county data showed 40 confirmed heat-related deaths so far this year with the hottest months still ahead, according to reporting by Scripps News. Counties that invest in dedicated heat-death investigation find more deaths. Counties that do not, do not.
Nighttime Is Where the Danger Compounds
Forecasters flagged one detail that carries more clinical weight than the afternoon peak. Morning lows in Las Vegas and Phoenix were expected to drop only into the 90s.
The body clears accumulated heat stress overnight. When the overnight low stays in the 80s or 90s for several consecutive days, that recovery does not happen, and each successive afternoon starts from a higher baseline. This is the mechanism behind the pattern that emergency physicians see repeatedly, in which heat deaths cluster on day three or four of a wave rather than on day one.
It is also why a fan alone stops working above a certain temperature. Moving hot air across skin accelerates fluid loss without producing meaningful cooling once the air itself is near body temperature.
The households at greatest risk are therefore not the ones without air conditioning in the abstract. They are the ones where a unit exists but is not being run, most often because of what it costs.
Cooling Help Exists, but Not in Every State and Not All Summer
The federal backstop for that problem is the Low Income Home Energy Assistance Program, and its coverage is uneven in ways that matter during a week like this one.
LIHEAP allows states flexibility to fund cooling assistance, summer crisis assistance, and year-round crisis assistance, and the Department of Health and Human Services describes those funds as intended to maintain cooling service, prevent shutoffs, and restore service after disconnection. Payment goes directly to the utility rather than to the household.
The limits are structural. Not every state offers a cooling component, application windows are short, and some close before the hottest weeks arrive. Oklahoma Human Services stopped accepting summer cooling applications on July 17, more than two weeks before this heat dome formed. Households facing a shutoff notice should ask specifically about crisis assistance, which in most states is funded separately and remains open year-round, and many utilities pause disconnection while a crisis application is pending.
Local cooling centers, public libraries, and mall hours remain the fallback for people who cannot cool their homes at all. County and city health departments publish current locations, and those listings change day to day during an active event.
Symptoms That Separate Discomfort from an Emergency
Heat exhaustion generally presents with heavy sweating, cold and clammy skin, weakness, nausea, headache, muscle cramps, and dizziness. Moving to a cool place, loosening clothing, sipping water, and applying cool cloths is the standard response, and symptoms that worsen or persist beyond an hour warrant a call to a clinician.
Heat stroke is a different event and is a medical emergency. The warning signs include a body temperature at or above 103 degrees, skin that is hot and red and often dry rather than sweaty, a rapid and strong pulse, confusion, slurred speech, and loss of consciousness. The correct action is to call 911, move the person somewhere cooler, and begin cooling with cool cloths or a cool bath while waiting. Do not give fluids to someone who is confused or unconscious.
Risk is not evenly distributed. Adults over 65, infants and young children, pregnant people, outdoor workers, people with heart or lung disease or kidney disease, and people taking diuretics, some blood pressure medications, or certain psychiatric medications face elevated danger. Anyone on a prescription who is worried about heat should raise it with the prescribing clinician rather than adjusting or skipping doses.
The most useful thing most readers can do this week costs nothing. Check on an older neighbor or relative living alone, in person if possible, and check again in two days. Heat deaths in older adults are frequently discovered late, and a phone call does not reveal a home that is 95 degrees inside.
Forecasters expect some relief in the northern Rockies early in the week, while the Southwest and Great Basin are likely to stay above average into the second week of August. MedicalDaily will monitor National Weather Service alerts and county health department death tallies as the event develops.
Frequently Asked Questions
How many people are affected by the current alerts? About 55 million people were under heat alerts across the West, concentrated in California, Nevada, and Arizona but extending north to the Canadian border.
How many Americans die from heat each year? CDC death-certificate data recorded 2,415 heat-related deaths in 2023 and 2,394 in 2024. Researchers consider these counts undercounts, because heat often kills by worsening an existing heart or kidney condition that is listed instead.
Is a fan enough? Not once air temperature approaches body temperature. Above that point a fan accelerates fluid loss without producing meaningful cooling. Air conditioning, a cooler location, or cool water on the skin is needed.
Why do overnight temperatures matter? The body clears accumulated heat stress overnight. When lows stay in the 80s or 90s for several consecutive nights, that recovery does not occur, and risk builds day over day.
What is the difference between heat exhaustion and heat stroke? Heat exhaustion typically involves heavy sweating, clammy skin, weakness, and nausea. Heat stroke involves a temperature at or above 103 degrees, hot skin that is often dry, confusion, and possible loss of consciousness. Heat stroke requires calling 911.
Can I get help paying a cooling bill? Possibly. LIHEAP funds cooling and crisis assistance, though not every state offers a summer cooling component and some application windows close mid-summer. Households with a shutoff notice should ask their state agency specifically about crisis assistance, which is usually available year-round.
Who is most at risk? Adults over 65, infants and young children, pregnant people, outdoor workers, and people with heart, lung, or kidney conditions. Certain medications, including diuretics, also raise risk.
