Extreme Heat Warnings Stretch From the Plains to the Desert Southwest as Labor Day Weekend Ends

Extreme heat warnings and advisories covered a wide swath of the country on the Labor Day holiday, from Kansas and Missouri to the deserts of Arizona and Southern California, as a stalled ridge of high pressure kept afternoon heat index values above 105 degrees Fahrenheit in multiple states. The National Weather Service office in Topeka issued an Extreme Heat Warning for 23 counties in central and northeast Kansas at 1:33 p.m. Monday, forecasting heat index readings up to 109 degrees through Tuesday evening. Similar warnings were in effect in western Missouri, while separate Extreme Heat Warnings covering the Phoenix metropolitan area, Yuma and the deserts of Southern California were set to remain active through Thursday or Friday.

The warnings arrived at the close of a holiday weekend that drew tens of millions of travelers onto highways and through airports, layering heat risk onto the ordinary hazards of a busy long weekend. News organizations tracking the National Weather Service's alert map, including CBS News, put the number of Americans under some form of heat warning or advisory at more than 50 million across roughly seven states, with California, Arizona, Kansas, Missouri, Oklahoma, Texas and Arkansas all carrying active alerts at some point during the day.

Numbers behind the warnings

Forecasters attached specific, measurable thresholds to each alert rather than general heat concerns. In the Kansas City forecast area, the National Weather Service projected heat index values up to 106 degrees; in southeast Kansas and southwest Missouri, up to 107 degrees. In the Phoenix and Yuma areas, the Weather Service's Extreme Heat Warning, first issued Monday morning and extended through Thursday or Friday depending on the zone, called for afternoon temperatures of 104 to 112 degrees. The Coachella Valley, San Diego County deserts and San Gorgonio Pass were placed under a warning through 8 p.m. Friday, with highs up to 110 degrees and overnight lows only in the mid-80s to low 90s — a detail meteorologists flag because nighttime heat that never breaks gives the body little chance to recover.

Beyond the warnings themselves, the National Weather Service issued lower-tier Heat Advisories across parts of Kansas, Missouri, Oklahoma, Arkansas, Texas and California, extending the affected footprint into Wednesday and Thursday in some coastal and inland Southern California zones. The pattern is not a single-day spike: several of the advisories in the Southwest run four or five consecutive days, a duration the Weather Service treats as its own risk factor because heat-related illness accumulates with repeated exposure and interrupted rest.

A ridge of high pressure with nowhere to go

The immediate cause is a ridge of high pressure that has parked itself over the central and southern Plains and the Mississippi Valley since before the holiday weekend began, trapping hot, humid air in place. A weak cold front pushing south and east has brought some relief to parts of the East over the past several days but has largely stalled before reaching the Gulf Coast, leaving the core of the heat dome intact over Texas, Oklahoma, Kansas, Missouri and Arkansas. The pattern is a stubborn one: with the front not expected to clear the Plains until midweek, temperatures there are likely to stay elevated even as neighboring states see gradual improvement.

The late-season timing matters. Heat waves that arrive in September, after schools have reopened and outdoor workers have shifted into fall routines, tend to catch people less prepared than the widely publicized heat domes of June and July. The Centers for Disease Control and Prevention notes that hot days are linked to more emergency department visits and hospitalizations for heat illness, cardiovascular and respiratory disease, and kidney disease, and that the risk does not disappear once summer vacation ends.

Who faces the greatest risk

Federal health guidance identifies a consistent set of vulnerable groups: infants and young children, pregnant women, adults over 65, people with disabilities, and anyone managing a chronic illness. The CDC also flags outdoor workers, athletes, people without stable housing or air conditioning, and socially isolated residents of low-income urban neighborhoods, where heat islands of pavement and rooftops can run several degrees hotter than surrounding areas. Certain medications compound the danger by reducing the body's ability to sweat or by increasing sun sensitivity, while heat itself can degrade insulin and some inhalers if left in a hot car or unrefrigerated bag.

Outdoor labor is a particular focus this week. The federal Occupational Safety and Health Administration has no permanent heat standard on the books — a proposed rule has been stalled since public hearings closed in 2025 — but the agency's heat-focused National Emphasis Program directs inspectors toward high-risk industries, including construction, agriculture and warehousing, on any day the National Weather Service issues a heat advisory or warning, which this week includes nearly the entire program's target region.

The scale of the annual toll is documented in federal mortality data. A CDC report published earlier this month put the 2024 total at 2,391 heat-related deaths nationwide, with the highest share, just over one-fifth, among adults ages 65 to 74. Researchers who study the data caution that the true toll is likely higher, since heat is often a contributing rather than a listed cause of death, masked by the cardiovascular or respiratory failure it triggers.

Take extra precautions when outside. Wear lightweight and loose fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke. Do not leave young children and pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes. Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.

That instruction, issued by the National Weather Service alongside Monday's Kansas warning, is boilerplate language the agency attaches to nearly every Extreme Heat Warning it issues nationwide — a sign of how routine, and how consistently dangerous, these conditions have become.

What happens next

Relief is uneven and, in places, still days away. The Kansas and Missouri warnings are set to lift Tuesday evening as a frontal boundary finally works through the Plains, bringing scattered thunderstorms and a modest temperature drop. The Southwest will not see the same break: the Phoenix-area and Southern California desert warnings extend through Thursday or Friday, and coastal Southern California is expected to heat up further midweek as advisories there begin later and run longer than the initial round announced Monday.

The Weather Service's standing advice applies regardless of location: postpone strenuous outdoor activity to early morning or evening, drink water rather than caffeinated or alcoholic beverages, never leave children or pets inside a parked vehicle even briefly, and check on elderly neighbors or relatives who may not have working air conditioning. Signs of heat exhaustion — heavy sweating, cold or clammy skin, dizziness and nausea — call for moving to a cool space and hydrating; confusion, a rapid pulse and hot, dry skin signal heat stroke, a medical emergency that requires calling 911. Local cooling centers, where available, are typically listed through county or city emergency management offices rather than the Weather Service itself, and residents in affected counties were being urged to check with local authorities for the nearest option.