An insulated lunch bag beats a separate cooler

An insulated lunch bag is all you need, as long as you pack it like a tiny cooler.

The trick is to use frozen things as ice packs. Freeze a water bottle or a juice box the night before, stick it in the bottom of the bag, and it keeps everything cold for hours. Bonus: by lunchtime you’ve got a cold drink. Ice gel packs work too, but frozen drinks pull double duty.

Then pack deliberately. Cold items should all go together, like they’re huddling for warmth — in this case, coldness. Put the lunch bag in the shade when you get to the picnic, and don’t stand there with the zip open while you decide what to eat. Every open is a sigh of warmth.

If you’re worried about raw chicken or something that spoils fast, that’s the one time I’d say bring a real cooler. But for sandwiches, fruit, cheese, and salads, a good insulated bag with a frozen bottle will do the job just fine.

Your potato salad will survive the afternoon.