Bummer in the Summer

Wine Needs Sunblock Too

We all know the general warnings about keeping wine safe from heat, but as summer temperatures swell, what does this mean in practice? Surely a bottle can survive an afternoon in the back seat of the car, or a couple weeks in a sultry apartment?

In fact, heat is probably wine’s biggest enemy, causing changes to its appearance, aroma, and flavor within hours. Because of the prevalence and subtlety of heat-related damage, it’s often chalked up to other causes.

Rather than tasting corked, heat-damaged wine might have oxidative notes, a brownish tint, aromas and flavors of stewed fruits (think “jammy” but in an unpleasant way), and an overall flat and faded quality. If it’s a bottle you’re unfamiliar with, it’s easy to fault the wine, rather than how it’s been stored.

Liquids expand when heated, and contract when cooled. As wine heats, it can nudge the cork up into the capsule, or the wine can seep around the cork. As it cools (and extreme temperature fluctuations are worse than small and gradual changes), the contraction of the wine creates a vacuum effect that can allow oxygen to enter the bottle through the cork.

Even if you live in an area with relatively mild summer temperatures, The National Highway Traffic Safety Administration determined that in 83 degree weather, even with windows cracked, a car can reach 109° in just 15 minutes. Even with outside temperatures in the mid-60s, cars parked in direct sunlight can reach temperatures in the 110s.

A study by Napa’s ETS Laboratories showed that just 36 hours of exposure to 80° (Fahrenheit) caused permanent changes to the chemical structure of tested wines. These changes occurred in just 18 hours of exposure to 86°, and just six hours at 102°.

So what to do? Generally speaking, during periods when it’s impossible to store your wine properly, keep it below 75 degrees and away from sunlight. Note that bottles made of colored glass, meant to protect the wine from light, can actually have the reverse effect in warm weather, absorbing heat and hastening damage to the wine. Heat rises, so a cupboard or attic that’s cool in winter may be a sauna in summer. Avoid having wine shipped during the summer, unless the sender can guarantee insulation from the elements; many wine sellers will provide free storage until the warm weather passes.

Most importantly, avoid disappointment altogether—nothing brings down a perfect summer day like a coveted Bandol rosé that tastes like watered-down prune juice. Find the best storage solution for your space and budget, and let your biggest stress this summer be which SPF to use.