MINNEAPOLIS — On Wednesday Ross Nelson trudged outside at 3 in the morning to check the temperature in his apple orchard. He went back out at 6, and again at 7. And then he got a call.

A customer was worried about the cold weather’s effect on Nelson’s Apple Orchard in Webster, which gives apple-picking visitors wagon rides to its trees in the fall.

“Probably for the first time in the 37 years we’ve been in business, we will not be open (in the fall),” Nelson said he told the customer. “They thought it was terrible,” he said.

Nelson has seen temperatures dip as low as 17 degrees on his 10 or 15 acres, where he grows 24 apple varieties. All over the state, a warm spring start has led to early apple buds now vulnerable to the recent cold. Nelson and other growers are concerned much of their crop will be killed off, leaving them without a paycheck and their customers without the crunchy Minnesota staple.

“I’ve never dealt with (this) in my life, my career,” Nelson said.

Ralph Yates, secretary of the Minnesota Apple Growers Association, said that it will be several weeks before growers will know the extent of damage to the apple crop.

Apple growers with budding trees start sweating when thermometers sink to 28, said David Bedford, a research scientist and apple breeder at the University of Minnesota. At that temperature, trees can lose up to 10 percent of their buds. Just a tad lower at 25 degrees, he said, and they can lose 90 percent.