Wine really has a love-hate relationship with heat. Grapes need heat to grow and ferment, but once the wine is bottled it needs to stay far, far away. I’m sure you’ve heard this, along with all the rules on how to serve wine at the right temperature. Today we’re going to talk about what happens to wine when it gets hot and give you some tips for handling situations when it’s likely to get a little warm.

Grapes need heat

Heat is necessary for grapes to grow. Some grapes prefer a cool or moderate climate, but they all still need a certain amount of heat and sunlight to ripen. Other grapes absolutely will not ripen if they don’t get enough heat, like Zinfandel and Cabernet Sauvignon. When grapes don’t ripen fully their fruit flavors struggle to develop. This results in wine that tastes a little less fruity than you would expect and unpleasant vegetal notes are more prominent. Many wines have a touch of vegetal notes, but it’s usually not great when they’re front and center.

When this happens (because sometimes the weather’s just a little too cool) some winemakers can try to compensate by blending with other varietals or grapes from other vineyards. This isn’t always possible, though, so sometimes they’ll use the grapes to experiment or just roll with it.

Fermentation is another time when heat is very important. Fermentation won’t take place without temperatures because the yeast won’t be able to eat the sugar in the juice and convert it to alcohol. There’s a fine balance, though, because you don’t want the yeast to eat the sugar too fast.

Heat is wine’s best friend when it comes to getting the wine to the bottle. Once it’s there, though, the relationship changes dramatically.

Heat + Bottled Wine = Sour Grapes

Once wine is bottled, it wants to be kept cool and out of the sun. You know how it feels like when you’re sitting near a window with the sun streaming in or sitting in a hot car without the A/C on? It’s pretty darn unpleasant. That’s how wine feels when it gets hot or has the sun shining on it, too.

In the wine world, a “hot” temperature is over 70 degrees for a prolonged period of time. Now, this doesn’t mean that a bottle of wine on the counter in your 75 degree house is going to spoil before you can drink it, but it will age slightly faster than it would at 50 degrees. For most wine this is no big deal; it really becomes important if you’re laying down bottles to age or you spent a lot on a bottle. I actually just recently got a wine fridge (I know! I can’t believe it took so long, either) so I can say on pretty good authority that most of your standard wine will be okay for a year or two in the low 70s, so don’t worry too much. As long as you keep the wine out of the sun and don’t stick it next to your furnace you should be fine. I used to keep mine in a lower cabinet so it was safely out of the way. Oh, and don’t turn off your A/C during the day in the middle of the summer if you live in the south, unless you like coming home to cooked wine.

You’ll know your wine has been overheated if the cork is pushed up significantly. This is the result of the liquid expanding as it is heated. Corks can also dry out and shrivel up in dry climates. Even if the cork doesn’t give it away, you can taste the difference. The tannins will be more noticeable than they should be and it will seem astringent. The fruits will be more muted and the wine color may be more brown than normal.

Wine on the move

One of the most critical times for wine is when it’s in transit. Whether the wine is moving from the winery to a distribution center or the grocery store, or you’ve picked it up and are taking it home, wine can easily get overheated when it’s on the move, especially in the summer. Some wine shippers will not ship when the temperature is above a certain point along the shipping route, while others pack ice packs into the boxes to help compensate for the weather. Wine can also be shipped overnight to help reduce the time in transit.

If you’re picking up wine at the store, try to make that your last errand on your way home so it doesn’t have to sit in the car while you run in and out of other places. If you’re taking it to a friend’s house but have to go somewhere first, take some ice packs and store it out of the sun or chill it before you leave so it will take more time to heat up. Temperature changes like that aren’t great for wine but won’t do too much damage if you’re opening the bottle in the near future.

Heat really isn’t something to fear when it comes to wine, but you definitely need to be aware of it. It just takes a little bit of forethought to keep your wine protected and safe until you’re ready to drink it.