A heat dome parked over the Southern Plains is breaking daily records across Texas and Oklahoma this week, with forecasters expecting the pattern to hold into next week. This is the back half of August producing readings more typical of its worst stretches, and it is not passing quickly.
The number that matters is not the daily high. It is how little the overnight low drops, because that is what turns a hot week into a dangerous one.
What a Heat Dome Is
A ridge of high pressure sets up and stalls over a region. Air sinks underneath it, and sinking air compresses and warms. The same high pressure suppresses cloud formation, so sunlight reaches the ground unfiltered day after day.
The mechanism is self reinforcing, which is why these events persist. Dry ground heats faster than moist ground, and the drier it gets the more efficiently each day of sun raises the temperature.
The Overnight Low Is the Real Threat
Human bodies recover from heat at night. When the overnight low stays in the upper seventies or eighties, that recovery does not happen, and heat stress accumulates across consecutive days.
This is why multi day events are far more dangerous than single hot days, and why heat kills more people in the United States annually than any other weather hazard. The danger builds quietly across a week rather than arriving in one dramatic afternoon.
Who Is Actually at Risk
Older adults, infants and small children, people with heart or lung conditions, and anyone taking medications that affect temperature regulation or fluid balance. Diuretics, some blood pressure medications and several psychiatric drugs all fall in that category.
Outdoor workers are the group most exposed and the least able to opt out. Construction, agriculture, roofing and delivery work all continue through heat events, and the people doing that work carry the largest share of the risk.
The Warning Signs to Know
Heat exhaustion looks like heavy sweating, cool clammy skin, weakness, nausea, headache and a fast weak pulse. The response is to get out of the heat, cool down and drink fluids.
Heat stroke is a medical emergency and looks different. Body temperature above 103 degrees, skin that is hot and often dry, confusion or altered mental state, and a rapid strong pulse. Call 911 and start cooling immediately while waiting. The distinction between the two is the most useful thing anyone can carry into a week like this.
What Actually Helps
Air conditioning is the intervention that works. If you do not have it, public cooling centers, libraries and shopping centers all function, and spending even a few hours in cooled air meaningfully reduces accumulated heat stress.
Fans alone stop helping once air temperature climbs past roughly 95 degrees, because moving hot air over skin no longer cools it. Cool showers, wet cloths on the neck and wrists, and shifting outdoor activity to early morning cover most of the rest.
The Grid Question
Sustained heat drives electricity demand to its annual peak, and Texas in particular has a grid that has drawn national attention during extreme weather in both directions.
Demand rising is not the same as a grid failing, and most heat events pass without incident. But it is the reason conservation appeals appear during these stretches, and following them is genuinely useful rather than symbolic.
Pets and Vehicles
Asphalt reaches temperatures that burn paw pads well before it feels dangerous to a person in shoes. The standard test is to hold the back of your hand on the pavement for seven seconds. If you cannot, a dog cannot walk on it.
Never leave any living thing in a parked car. Interior temperatures climb far faster than most people expect, and cracking the windows does close to nothing. Compounding weather risk has been a running theme this month, including in our coverage of the Hawk Fire outside Reno.
What to Watch This Week
Watch overnight lows more than daily highs, because that number tells you whether the risk is accumulating. Watch for excessive heat warnings from your local National Weather Service office rather than national summaries.
Watch the pattern’s exit as well. Heat domes break when the upper level ridge shifts or erodes, and forecasters generally see that coming several days out.
There is a distinction in the forecast products worth knowing, because the terms get used interchangeably and mean different things. A heat advisory signals conditions that are dangerous for vulnerable groups. An excessive heat warning signals conditions dangerous to anyone, including healthy adults, with prolonged exposure.
A watch, as with other hazards, means the conditions are possible rather than expected, and it is the point at which preparation should happen rather than the point at which people should be reacting.
The heat index is the other number to read correctly. It combines temperature and humidity to describe what the air actually does to a body, and in humid conditions it can run well above the thermometer reading. In this part of the country the index is frequently the number that matters.
Frequently Asked Questions
What areas are affected?
The Southern Plains, with Texas and Oklahoma in the bullseye. Records are being broken this week and the pattern is forecast to persist into next week.
What is a heat dome?
A stalled ridge of high pressure that causes air to sink and warm while suppressing clouds, allowing unfiltered sunlight to heat the ground for days on end.
Why do overnight lows matter?
The body recovers from heat overnight. When lows stay very warm that recovery does not happen and heat stress accumulates across consecutive days.
What is the difference between heat exhaustion and heat stroke?
Heat exhaustion brings heavy sweating, cool clammy skin, weakness and nausea. Heat stroke is an emergency: temperature above 103 degrees, hot skin, confusion, rapid strong pulse. Call 911.
Do fans help?
Only up to a point. Once air temperature passes roughly 95 degrees, moving hot air across skin no longer cools it effectively.
How do I know if pavement is too hot for a dog?
Hold the back of your hand against it for seven seconds. If you cannot keep it there, it will burn paw pads.
