(PD) - Grapes around the North Coast are slowly turning color as a precursor to this year’s harvest, which is expected to arrive earlier than usual and deliver a smaller crop than last year.

Vineyard managers in Sonoma and Napa counties report that they have seen signs of veraison — the French term for the onset of the visual signs of ripening in grapes. During the process, which begins the countdown to harvest, red grapes turn from green to red and a purplish hue while white grapes go from green to a golden yellow.

Local farmers said this year’s crop is maturing anywhere from 10 days to two weeks earlier than typical, similar to last year’s timeline, which resulted in the earliest harvest on the North Coast in a decade. Harvest is on track to start in mid-August, though fruit destined for sparkling wines will begin coming off the vines in late July or early August.

In fact, grower’s feared harvest would occur even sooner this year following a mild winter that triggered an unusually early bud break, when the vineyards awaken from their winter slumber. Most vines finished bud break in February, more than a month earlier than normal.

However, cool weather in May slowed down flowering and fruit set, when small flowers on the vines are fertilized and transformed into tiny grapes. Typically, this stage can last from 10 to 14 days. This year, it stretched out as long as four weeks in some cases, growers said.

As a result, growers expect the size of the Sonoma County grape crop will decline for the second straight year from the record-breaking 2013 harvest. Last year, growers hauled in 255,635 tons of grapes, valued at $593 million.

“We saw a long bloom because of a cool May,” said Ryan Decker, wine grower relations manager for Rodney Strong Vineyards in Healdsburg. “The main effect is you will see a reduced berry set, which is going to reduce yield a little bit, which is what we are seeing. … It’s just a little under the long-term average.”

Barry Hoffner, owner of Silverwood Ranch in the Pine Mountain/Cloverdale Peak area that borders Sonoma and Mendocino counties, thinks his crop will be 15 to 20 percent smaller than last year on the 40 acres of mountain vineyards he owns and leases.

“I don’t think it is going to affect the quality,” Hoffner said.

Growers are monitoring their grapes to spot signs of unevenness among fruit that is ripening slower than other clusters because of the long flowering period, likely forcing them to thin some of the crop this year.