How Rain Impacts Wine Grapes

With all this rain we’ve been experiencing across Iowa this whole week (UGH! Bring back the sun!), you might wonder, how does rain impact wine grapes right before harvest? Well, let’s discuss!

First off, can we all agree that days on end of rainy weather gets old reeeeeeal fast?! I mean, we really did need some rain in Iowa, but as they say, when it rains, it pours! Mmmkay, now that we got that out of the way, we all know that we need rain for a lot of reasons…. just not too much. Or too little. Yeah, it’s a tricky balance to achieve, and most years we just don’t get the perfect balance here in Iowa.

As we get in the weeks just prior to harvest, in early to mid August, if we have a cold front or a period of lengthy cloud cover or overcast weather, the grapes will have a hard time ripening properly without the good ol’ sunshine. Grapes need sunlight and it’s especially important around or just before harvest time. But even further, if it rains in the weeks or even days prior to harvest, the grapes will take on more water, which means the flavors become diluted and it messes with the sugar to acid balance that winemakers use to achieve that delicious wine you’ve come to experience and love. In years of drought (sort of like this year in parts of Iowa un until this past week….) established grapes tend to do better, and the flavors within those clusters of berries tend to concentrate and have a much more intense flavor for winemakers to work with, resulting in much higher quality wines oftentimes. Also with too much rain, grapes start to swell up and can even split, which can cause premature spoilage on the vines and mold/mildew problems in the vineyard.

While we’re on the topic, rain is also a concern in the spring. Like many plants, grapes are formed from flowers, so a heavy rain in the flowering stage can knock the blooms right off the plant. No little grape flowers = no little (or big) grapes. A wet growing season can affect the taste of a wine and can also lead to mildew and other diseases in the vineyard, especially in Iowa where growers tend to have to spray for disease frequently due to damp or humid conditions.

So yeah. Rain isn’t always a good thing (talking to you, Luke Bryan).

But I mean, grapes DO need rain. Only sometimes. But like juuuuust the right amount. And at the right time of year. Growing grapes isn’t for the faint of heart, and it’s truly a labor of love (and occasional prayer!). Now you know how rain affects the grapes going into your glass of wine!

Cheers!