PASO ROBLES, Calif. – Wild spring weather across California’s wine country has been enough to drive a vintner to drink.

From killer snow in the Sierra Nevada foothills to dry-season downpours along the coast to a hard freeze in temperate Paso Robles, 2011 is proving a challenging vintage.

“That’s what makes this business so damned interesting,” said Jim Fiolek, executive director of the Santa Barbara County Vintners’ Association.

It also can keep winemakers up at night.

Jason Haas, general manager of Tablas Creek Vineyard near Paso Robles, said winemaker Neil Collins has experienced many sleepless nights this spring.

“These people who envy the winemaker’s lifestyle should drive around here with Neil at 3 a.m. when he knows it’s freezing and there’s nothing he can do about it,” Haas said.

Vintners have long joked that the weather is just like last year — different. But people expect to find constants in the nation’s premiere grape-growing state.

Rain is expected to taper in April and end by May, then not return until November. In those months, balmy temperatures awaken dormant vines from their winter slumber and buds start to break.

This year there has been frost and record rain in June. Sustained temperatures over 70 didn’t hit until last week in most wine regions.

Now just days before the official start of summer it looks like early spring across California wine country. Buds are just emerging and the fruit is forming far behind schedule.

“This weather is causing all kinds of problems, but it’s not the first time and not the last,” Fiolek said. “Other products have a more ephemeral lifetime, but ours goes on and on and tells the story of the weather pattern.”

While rain is good for some crops, late precipitation is not for California’s $18.5 billion wine industry. Regulating water controls the intensity of grape flavors — and too much causes mildew.

The most recent deluge last Sunday and Monday across Napa and Sonoma forced crews back into some fields, where they hope that removing select leaves will fight mildew by increasing airflow.

It’s snow, not rain, that caused problems in mountainous El Dorado County, where leafing vineyards have been hit by the same spring snow storms that have some ski resorts dreaming of remaining open through July 4.

“There’s nothing we can do about it, and we don’t even know the outcome yet,” said Josh Bendick, winemaker at Holly’s Hill in the Sierra-Nevada foothills, where 4 inches accumulated May 15 on shoots of a white wine-grape.