My friend broke down on a desert highway in Nevada last August. No shade, no water, no cell signal. He had a spare tire and jumper cables — the winter kit stuff. What he needed was water, sunscreen, and a way to signal for help. None of those were in his car.

Summer road trips need a different emergency kit than winter ones. Here is what you actually need.

Water — way more than you think

Pack at least one gallon of water per person. Car trouble in summer heat means you could be waiting hours for a tow. Dehydration sets in fast. Rotate the water out every few months because plastic bottles degrade in heat and the water starts to taste like the bottle.

Also pack electrolyte tablets or powder packets. Water alone is not enough if you are sweating heavily.

Sun protection and shade

Sunscreen. A wide-brimmed hat. A lightweight long-sleeve shirt. If you are stuck outside your car on a shadeless highway, sunburn can blister you in under an hour. A cheap tarp or umbrella in the trunk gives you instant shade if you have to wait outside the vehicle.

If you must stay inside the car with the engine off, crack the windows and put up a windshield sunshade. The interior of a parked car can hit 140°F in direct sun.

Signaling and communication

Road flares or LED flashers. A bright-colored bandana or cloth to tie to the antenna. A portable phone charger that you actually keep charged. The one in your glove box that has been dead for six months does not count.

Write down the phone number for roadside assistance on paper. If your phone dies, you cannot look it up. Old school, but it works.

The stuff nobody thinks about

Jumper cables — batteries fail more often in extreme heat than in cold. Duct tape — temporary fix for a loose hose or a cracked mirror. A multi-tool — you will need pliers or a knife at the worst possible moment. Cash — small bills, enough for gas and a meal, because card readers go down and small-town stations sometimes do not take cards.

A physical map of the state you are driving through. GPS fails when there is no signal. A paper map weighs nothing and never runs out of battery.

Baby wipes. Not just for babies. When you change a tire in 100-degree heat and your hands are covered in brake dust and sweat, baby wipes are the best thing in the world.

My friend waited three hours for a tow on that Nevada highway. He had no water. A passing driver gave him a warm bottle from their own car. He now keeps a full emergency kit in his trunk and texts me photos of it every time he restocks.