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Summer outings to the beach could be fun, but they also could be really hot. That’s especially true if you live somewhere like Florida where temperatures can flirt with 90 degrees Fahrenheit on a toasty day. On such days, there’s nothing better than a cold drink, something to reduce the heat and also help you unwind. But with the sun actively working to turn your iced tea into boiling chai, the best way to transport your drinks and keep them cold at the same time is a cooler. 

That said, it’s one thing to have a cooler outside on a hot day with some breeze, but another thing entirely to keep it locked up in a car that’s also in direct sunlight. We all know how hot a car can get when it’s in the sun; it’s basically the greenhouse effect on wheels. Sunlight goes through the car glass and hits the upholstery, causing it to absorb and radiate some of that heat, but since the heat coming off the upholstery is longwave infrared radiation, it doesn’t go through glass as efficiently as the shortwave radiation from the sun. The result is that the car keeps getting hotter, as it doesn’t lose heat fast enough. So, a 90-degree day could turn your car into a 150-degree furnace in an hour and possibly damage some items you left in it

The real question now is, can a cooler withstand that? The short answer: yes. The long, more accurate answer: it depends on the quality of the cooler, where you kept it, and how much ice you packed.

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Step one in preparing a cooler for a hot car is getting a good cooler to begin with. Unless it’s not staying in the car long, a badly-insulated $5 cooler you got from Walmart won’t cut it. Maybe you’ll be able to pull off about 4 hours with proper placement and a lot of ice, but quite frankly, those are meant for short, easy trips. You’ll have to get a little more serious with your cooler selection.

Sadly, there’s no standardized cooler insulation metric like we have for fridges or sleeping bags. Manufacturers do their own tests and tell you how many hours their product will keep your drinks cool, which, as you know could be a conflict of interest. Your best bet is to get a big cooler with manufacturer-rated long hours and good reviews — although they won’t come cheap. This SlashGear-highlighted 45-quart Ninja FrostVault cooler is a strong candidate for such a cooler; it could add a whole 24 hours to how long your drinks stay cool in a hot car. You can also try any of the US-made cooler brands and get one with at least 45 quarts of space and sterling reviews.

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The next step is ice — pack lots of it. That’s why we recommend bigger coolers, it leaves more space for both ice and drinks. Try to make sure there’s as little air in your cooler as possible. Air gets hot faster than solid ice, so you want to make sure your cooler has ice in every empty spot you can plug. It also helps if you pre-chill or even freeze your drinks before putting it in the car. That way, it will be able to fend off heat better.

Lastly, you have to slow the warming of the cooler by placing it in the coolest part of your car: the trunk. Do not store it anywhere it might get direct sunlight; that will only speed up the warming process. Since the cabin of most cars have some sort of window, that automatically excludes it as a good place to store your cooler. Put in the trunk and throw a reflective blanket on top to preserve its temperature and provide additional insulation.

If you meet all these requirements, you could keep the items in your cooler cold for 24 hours or more in a car sitting at 100 degrees Fahrenheit.