The Fourth of July heat wave this year put more than 200 million Americans under some kind of extreme heat warning, watch, or advisory, according to NOAA’s Weather Prediction Center, with heat index values forecast as high as 115°F in parts of the Mississippi Valley and the Northeast. I spent that weekend at a backyard party where a friend sat down on the cooler, said she had a headache and felt “kind of off,” and then insisted she just needed a soda. That’s how heat exhaustion symptoms usually show up in real life. They look like an ordinary bad afternoon, and most of us wait for something dramatic before we take them seriously.
I’m not a doctor, and nothing here replaces one. But after reading the CDC’s guidance closely, I’m convinced the stage that matters most is the early, boring one.
Heat exhaustion symptoms are easy to explain away
According to the CDC’s National Institute for Occupational Safety and Health, heat exhaustion can bring headache, nausea, dizziness, weakness, irritability, thirst, heavy sweating, a higher-than-normal body temperature, and peeing less than usual. Read that list again and think about how many of those you’d blame on something else. A headache is the sun. Irritability is the kids. Nausea is the potato salad. Weakness is because you’ve been carrying folding chairs.
None of these feel like an emergency on their own, and when they come one at a time, it’s easy to talk yourself out of each one. Heat stroke is the scary one, with confusion, slurred speech, seizures, loss of consciousness, and a very high body temperature. NIOSH notes that body temperature in heat stroke can reach 106°F or higher within 10 to 15 minutes. By then you’re well past the point of handling things with a cold drink in the shade. Heat exhaustion is the stage where you still have room to fix it.
Women land in the ER for heat less often, which is no reason to relax
The CDC looked at heat-related emergency department visits from May through September 2023, the summer that set records for heat deaths. Across the warm season, the average rate for men was 271 heat-related visits per 100,000 ED visits. For women, it was 104. That gap mostly reflects who works outside in construction, agriculture, and delivery, but I don’t read it as good news for us. I read it as a sign that a lot of heat illness in women happens in places nobody counts: the garden, the sidelines of a soccer tournament, the farmers market, the hot kitchen with the oven on.
The same report found the highest rates in the South Central region (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas) at 483 per 100,000 ED visits, and adults 26 to 54 had the highest rate of any age group. In other words, the people most likely to end up in the ER for heat are working-age adults who think they’re fine.
What to do the moment you notice the first signs
NIOSH’s first aid steps for heat exhaustion are simple. Get out of the heat. Take off extra layers, including shoes and socks. Cool down with cold compresses, or wash your head, face, and neck with cold water. Take frequent small sips of cool water. And here’s the line people skip: NIOSH says to get the person to a clinic or emergency room for evaluation, and to call 911 if medical care isn’t available. Don’t leave them alone.
For heat stroke, call 911 right away, move the person somewhere cool and shaded, and cool them as fast as you can with cold water, wet cloths, or ice packs on the head, neck, armpits, and groin while you wait. Heat cramps are the milder cousin, with painful spasms in the legs, arms, or belly. NIOSH suggests water plus a snack or sports drink to replace carbohydrates and electrolytes, says to skip salt tablets, and advises medical help if the cramps don’t ease within an hour or if the person has heart problems or is on a low-sodium diet. If you take medication or have a health condition that affects how you handle heat, talk to your doctor before summer, not during it.
The hydration math for a two-hour afternoon outside
NIOSH’s heat stress guidance for people working in the heat is to drink 1 cup (8 ounces) of water every 15 to 20 minutes, and to stay under 48 ounces an hour. That’s roughly 24 to 32 ounces an hour. I find the per-hour number hard to picture, so here’s how it plays out on a normal summer Saturday.
Say you’re outside for two hours, from 10 a.m. to noon, weeding the garden or watching a tournament. At one cup every 20 minutes, that’s 6 cups, or 48 ounces, over the two hours. A standard 24-ounce insulated bottle holds 3 cups, so you’d want two full bottles, which most of us never bring. At the faster end, one cup every 15 minutes, it’s 8 cups, or 64 ounces, which is still comfortably below the 48-ounce-per-hour ceiling because it’s spread over two hours. If I only pack one bottle, I’m planning to drink about half of what that guidance suggests. That alone explains a lot of the headaches I used to blame on the sun.
Check HeatRisk before you check the high
The forecast high tells you how hot it’ll get. It doesn’t tell you how dangerous that heat is for your area. The National Weather Service and CDC built HeatRisk for exactly that. It rates each day from 0 (green, little risk) to 4 (magenta, extreme risk for everyone) and factors in humidity and local health data, because 95°F in Phoenix and 95°F in a humid Ohio July aren’t the same day. At level 3, red, CDC says most people are affected, especially anyone with long outdoor exposure. That’s the day I move the yard work to 7 a.m. or skip it.
I treat heat the same way I learned to treat heart attack symptoms in women: knowing the list doesn’t help much if you’re too polite to act on it. And while you’re planning the outdoor stuff, how much sunscreen you really need is the other number most of us underestimate.
The rule I’m keeping for August
August still has plenty of 95-degree days ahead of it. My rule is that two heat exhaustion symptoms at the same time means we stop, get inside or into real shade, cool off, and sip water. If symptoms get worse, last longer than an hour, or anyone seems confused, it’s a call to a doctor or 911, with no debate. It feels like overreacting right up until the afternoon it isn’t.