How to stay cool outside in extreme heat: what actually worked when we measured it

"Dad, your face is the color of a hot dog." That was my daughter, age nine, on the sideline of her brother's soccer tournament, and she wasn't wrong. The thermometer I'd clipped to our canopy pole read 99.2°F in the shade. There were three games left.

I test grills and outdoor gear for this site, which means I spend a lot of summer standing next to things that are hot on purpose. But this July's heatwave was different. Twelve days in a row above 95°F, most of them sticky, and a family that still needed to mow, weed, watch soccer and walk the dog.

So I did what I always do: I measured. Five neck fans, two tabletop evaporative coolers, three cooling towels, a pile of cotton bandanas and every free habit my neighbors swore by. Some of it cooled me down in a way I could see on the thermometer. Some of it only felt nice for a minute. And one gadget made me hotter. To understand why, you need about sixty seconds of science first.

The one thing to understand about heat

Your body cools itself mostly by sweating. But sweat doesn't cool you by being on your skin. It cools you by evaporating off your skin, and evaporation needs two things: dry air and moving air. That's why 95°F in Phoenix feels like a hair dryer and 95°F in Houston feels like breathing soup. Same number, very different afternoon.

There's a second number to keep in your head. On a hot day the skin on your arms and neck sits around 93 to 95°F. Moving air only takes heat away while it's cooler than your skin. Once the air is hotter than that, a fan starts blowing heat onto you instead of carrying it off.

Keep those two ideas in mind, dry air and skin temperature, because they explain almost every result below. Here's how we got those results.

How we tested it in a real heatwave

I clipped a digital thermometer with a humidity sensor to our back fence, in the shade, and logged it every hour from 8 a.m. to 8 p.m. For each product or trick, I measured the skin on the side of my neck with an infrared thermometer before and after ten minutes of use, sitting still in the shade. Then I did it again while working, because nobody buys a neck fan to sit still. My wife Tanya and our neighbor Luis, who roofs for a living, wore the same gear on their own days so it wasn't just my neck deciding.

Everything was bought at retail. Nothing got a pass for being cheap or expensive. And every test day got a note about the humidity, because as you'll see in a minute, that note turned out to matter more than the price tag. We start with the gadget everybody asks me about.

Neck fans: good until about noon

We tested five neck fans between $20 and $219, including the JISULIFE Neck Fan Pro (around $45), two no-name bladed models and the Torras Coolify, which adds a small electric cooling plate against the back of your neck. On a normal hot morning, 88°F with 44% humidity, ten minutes on medium dropped my neck skin temperature by an average of 3.8°F across the plain fans. That's a real, noticeable difference. Tanya kept hers on through two hours of weeding and asked me not to take it back.

At 101°F the story flipped. The same fans dropped skin temperature by only 0.9°F, and after twenty minutes it felt like standing next to a hair dryer on the low setting. That's exactly what the science predicts, and it matches the CDC's current advice that fans stop being safe cooling once the temperature is above 90°F.

"It's great until lunch. After that it's just moving the oven around your ears." Luis, after a morning on a roof

The Torras was the most interesting and the most expensive. The cooling plate really does get cold within seconds, and it's the only neck gadget that still felt good at 101°F. The catch is the battery: in cooling mode ours lasted 2 hours 40 minutes, not a full afternoon. It also weighs about 10 ounces, which you notice after a while. For a two-hour event, great. For a workday, bring a power bank.

Two practical notes from our week. The two bladed fans caught my daughter's hair twice in one afternoon, the bladeless ones never did. And every battery claim was optimistic: the fan sold as "up to 16 hours" ran 7 hours 40 minutes on medium. So a neck fan earns its place on warm days. On brutal days it needed help, and the help cost almost nothing.

The $3 combo that beat every gadget

I soaked a plain cotton bandana in ice water, wrung it out and tied it loosely around my neck. Then I put the neck fan on over it. At 101°F that combination dropped my neck skin temperature by 6.9°F in ten minutes. Nothing else we tried came close, including gadgets that cost fifty times more.

It works because you're doing your sweat's job for it. The fan finally has something to evaporate, and the wet fabric keeps giving it water long after your sweat has stopped keeping up. The bandana needed re-wetting every 20 to 25 minutes, right when it started to feel warm. On the soccer sideline I kept a spare in a zip bag in the cooler and swapped them every half hour.

So if you already own a neck fan, don't throw it out when the thermometer passes 95. Give it a wet bandana to work with. And if you don't own one yet, the cooling towel line in that table deserves a closer look.

Cooling towels: real, but not magic

Cooling towels, like the ones from Mission that sell for around $12 to $20, are thin, loose-weave fabrics made to hold water and let it evaporate fast. You wet them, wring them, snap them in the air and drape them on your neck. They worked well, 4.1°F at 101°F, and they did it without a battery.

Here's the part the packaging skips. The towel isn't chemically cold. The "snap to activate" move just helps extra water fly off so it evaporates faster. It's the same physics as my bandana, in a fabric that dries a bit more evenly and doesn't drip down your back. In our side-by-side, a cooling towel stayed useful for about 30 minutes, the bandana about 22.

So is it worth $15? If you're outside for hours, yes, because it's lighter, it doesn't drip and it packs flat in a pocket. If you're out for one soccer game, a cotton bandana you already own does most of the job. Either way, both depend on dry air to evaporate, and that brings us to the gadget that let me down.

Mini evaporative coolers: check the humidity first

These are the small boxes with a water tank and a wet pad that get sold as "personal air coolers" or even "mini AC." They are not air conditioners. They blow air through a wet pad, which is the bandana trick in a box. Their results depended almost completely on the weather. I measured the air 20 inches in front of each unit:

On the dry day, on a patio table pointed at my face, it was pleasant. On the 71% day it mostly added water to air that was already wet, and the porch felt stickier after an hour than before I turned it on. That's the one gadget that made me hotter.

If you live somewhere dry, like Arizona, Nevada or inland California, a small evaporative cooler can make a patio nicer. If your summers feel like a sauna, put that money toward a good neck fan, two bandanas and a cooler full of ice water. Gadgets aside, the habits cost nothing and several of them measured better than any box.

Free habits that showed up on the thermometer

• Do the hard stuff before 10 a.m. On July 17 it was 81°F at 8:30 and 97°F by noon. I mowed at 7:45. Same 52 minutes, half the misery.
• Stay off the concrete. At 2 p.m. our driveway read 139°F on the surface, the lawn a few feet away 96°F. Move the chairs to the grass and the kids' pool into the shade. Your dog's paws will thank you too.
• Cold water on your wrists. Thirty seconds under the garden hose dropped my wrist skin temperature by 8.2°F. Wrists, neck and the backs of your knees are where blood runs close to the skin.
• Drink on a schedule. The standard guidance for working in heat is about 1 cup of water every 15 to 20 minutes, and no more than about 48 ounces an hour. I set a phone timer, because once I'm busy I forget until I'm dizzy.
• A wide-brim hat, wet. A soaked cotton bucket hat cut the sun on my face and neck and worked like a small bandana for my head. It looked ridiculous. My daughter took a photo.

All of this is about staying comfortable. There's also a point where comfort stops mattering, and you should know where it is before you need it.

When to stop, no matter what gear you have

I'm a dad before I'm a tester, so this part is not optional. Heat exhaustion shows up as heavy sweating, cold and clammy skin, headache, dizziness, nausea, muscle cramps or weakness. If you feel that, stop, get somewhere cool, loosen your clothes, sip water and put cold wet cloths on your skin. If it doesn't improve within an hour, get medical help.

Heat stroke is an emergency. Confusion, slurred speech, hot red skin, a racing pulse or fainting mean you call 911 and start cooling the person right away, with water on the skin and shade. Kids, older adults and anyone on certain medications get into trouble faster than a healthy adult.

No neck fan changes those rules. If the heat index is above 103°F where you are, the best cooling gear is a building with air conditioning, even if it's the library or the mall for two hours.

My heatwave kit after all the testing

By the end of July my sideline backpack had settled into five things: a bladeless neck fan, two cotton bandanas, one cooling towel, a small cooler with ice water and a spray bottle for the kids. Total cost under $70 if you already own the cooler. The bulky evaporative cooler went back in the garage for the next dry spell.

We score all of this gear the same way, with days of real use and numbers we can check, as explained on our how we test page. The neck fans that did best are in our reviews once our longer battery test wraps up. And nights are their own fight: Rhonda logged 45 hot nights to figure out why heat wakes you at 3 a.m. and which fixes actually kept her asleep.

Questions readers asked us