Heatwave - Short Term Overheating of Wine
We all know that wine should be kept cool in order to age well. A wine that is allowed to heat up turns into vinegar. Think of a head of lettuce. If you keep the lettuce cool in the fridge, it stays green. If you leave it in the back yard on a 95F day, it wilts almost immediately. A fridge-cool beer can be perfect - while a beer sitting on the top of the grill for a few hours will be skunked beyond recognition. Wine is just the same way - it is a natural product, made from grapes, that is sensitive to heat.
The proper storage temperature for wine is around 55F - so not as cold as a standard refrigerator, but not as warm as most humans keep their homes in modern times. Remember that "Room Temperature" for the French was around 55F, back in the days of no central heating or insulation! They wore a lot of thick tunics :)
So, let's say you don't have central air conditioning in your home, and you get hit with a heat wave. You are storing your wines in your kitchen, not a cool cellar, and the kitchen spikes to 90F for three days in a row. What does this mean for your wines?
First off, the thing most damaging to wine is air. Wine and air turns into instant oxidation / vinegar no matter what temperature or humidity the wine is at. Check the cork. When the liquid in the bottle heated and cooled, it tugged the cork in and out. If liquid leaked out, or air leaked in, it could mean the wine is now vinegarry. If it does look like the cork seal was compromised, drink the wine soon and have a back-up on hand in case it is in fact now vinegar.
The "did the wine cook enough to damage it" is usually a much harder issue to quantify. There's no way to tell by looking at the bottle. The only real way to know is to taste it. If you had 6 bottles of your favorite house wine side by side on a shelf, it's likely that whatever happened to one happened to all of them. So open one! If it's bad, well, now you can cook with it or use it in salad dressing. If it's still good, enjoy the bottle you opened, and put the rest somewhere cooler so they aren't damaged further going forward.
Remember that in pretty much every situation of the bottle going up over 80F there will be *some* damage. But think of it like this. Say you buy a slice of Key Lime Pie from your favorite bakery and stick it, uncovered, in the fridge for 2 days. Now say you take that piece out, and put it side by side by a brand new piece of Key Lime Pie from that same bakery, bought fresh. If you compare those two pieces side by side, you probably taste a difference! Maybe the fridge one is a little staler, a little less flavorful. But if you had only eaten the leftover piece, you probably would have thought the flavors were quite nice. The slight "degradation" of flavor might not have even been enough to register.
So yes, the heated wine is going to be a bit tarter, a bit less aromatic, a bit more alcoholy. But will you really notice or even care? It depends on how keen your senses are, just how much the wine was heated, and to be honest if you even care. If I had a glass of delicious Arrowood viognier that had been spot-roasted for a day, it might still taste much better to me than say a cheap glass of $2.99 wine that was "perfectly stored".
Every single wine bottle is different from every other one, if you want to get down to it, because the grapes were different, the storage was different, the transportation conditions were different, the glass you used was different, and heck the length of time since you last brushed your teeth was different. Wine drinking is a rainbow of experiences all melding together, which is what makes it so much fun.
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