How Long Can Mayo Sit Out? (Because We’re Not Trying to Ruin the Barbecue with a Bad Potato Salad)

It’s a scenario we’ve seen too many times: You’re hosting a family barbecue and Aunt Doreen brings her famous potato salad. It’s creamy, dreamy and everything you want to pair with a hot dog, so of course you’re eyeing up a second helping…until you realize the bowl has been skulking around at the end of the table, sun beating directly onto those mayonnaise-dressed spuds, all afternoon.

So how long can mayo sit out, really? As it turns out, the life of this condiment is severely shortened by summer temps. According to the USDA, you have a measly two hours to party with that mayonnaise-based salad, but it’s a *little* more complicated than that. Here’s the sitch.

Welcome to Food Safety 101. In cooking, there’s a range of temperatures referred to as the “Danger Zone,” aka 40°F to 140°F. Bacteria love the danger zone, and they flourish in these temps (potentially doubling in at little as 20 minutes, per the USDA). We’re not talking cutie bacteria that are beneficial to your microbiome, but baddies like E. coli, salmonella and staphylococcus aureus—the villains threatening to ruin your alfresco fête (and also the rest of your weekend) with gastrointestinal distress.

With that in mind, food safety experts officially give you two hours to leave anyfood, including mayonnaise, out of the refrigerator. But there’s a catch: That’s at ambient temperatures below 90°F. Above that, and you’re given just one hour before foodborne illness becomes a threat.

Thankfully, your picnic menu isn’t totally sabotaged by the sun. It’s as easy as remembering this tip: Keep hot foods hot and cold foods cold. In the case of mayo-based salads (like potato, macaroni and coleslaw), you’ll want to ensure they stay below 40°F, whether by storing the bowl in a cooler or setting it over an ice bucket. It’s also a good idea to use a shallow serving bowl, which will allow for quicker, more even cooling than a deep vessel. And if you’re risk averse (no judgment), just return the salad to the fridge once everyone’s filled their plate.

Making dishes ahead of time is one of our love languages. But if you’re wondering exactly how far ahead you can prepare your mayonnaise-based mac salad, the answer is three to four days, according to the U.S. Department of Health & Human Services. And if you’ve made it the day of, you can safely return it to the fridge as long as it was not in the danger zone.

And with that, congrats—you just graduated to Food Safety 201, or “How to Keep Cousin Daryl from Double-Dipping in the Guac.”

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• BLT Pasta Salad

_{Katherine Gillen is PureWow’s senior food editor. She’s a writer, recipe developer and food stylist with a degree in culinary arts and professional experience in New York City restaurants. She used to sling sugary desserts in a pastry kitchen, but now she’s an avid home cook and fanatic baker.}