SONOMA COUNTY, Calif. (KGO) — In the North Bay, extreme heat is keeping grape growers in Wine Country on their toes. Harvest is in full swing and hot weather is adding an extra layer of concern about picking.

“It’s a very challenging time, you got to stay on it every day, all day,” said Steve Ledson.

Ledson’s family has been growing grapes in the Sonoma Valley since 1860. The job is never easy or predictable.

“This week we’ve been focusing on our Chardonnay and Sauvignon Blanc,” Ledson said.

Grapes are going into a giant press. The juice is collected below.

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Overnight, Ledson vineyard workers picked about seven tons of grapes.

This week, timing is everything.

Extreme heat spikes are fast-tracking the harvest.

Ledson says grapevines are a lot like the human body.

“When it gets hot, the grapevine shuts down, so if you get over 92 degrees, it wants to go to sleep,” Ledson said.

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Associate Winemaker Justin Schuchardt says the concern is dehydration and over-ripening.

“Heat poses a challenge. We want to get the fruit off the vine before heat can damage the fruit,” Schuchardt said.

Staying ahead of the weather and knowing when to irrigate is key. Out in the vineyard, Ledson was checking on his old vine Zinfandel grapes.

“It’s supposed to get cool now, which is good. Slows the ripening process,” Ledson said.

The Sonoma Valley Vintners and Growers Alliance says growing season always has curveballs.

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“Mother Nature is quite the force to contend with, so what the vintners and growers try to do it work with Mother Nature, she designates when things are happening,” said Alliance executive director Robyn Sebastiani.

Back at the crush facility, Ledson sampled the harvest.

“Tastes great, it’s going to be a great year. Enjoy the wine,” Ledson said.

Grape harvest is expected to last through October.