The cold and wet weather, which came in last week and seems to be sticking around for a little bit, is especially bad for potatoes, he said.
Once potatoes freeze, they're unsalvageable, Kreis said.
"They basically turn to mush in storage," he said.
And wet fields make it "nearly impossible" to get equipment in to harvest.
Some growers are done harvesting their potatoes, but others are only half done.
Bryan Folson, president of Folson Farms, said his business still has 43 percent of its crop in the ground.
And it is uncertain how harvesting them will go.
"It depends on how everything dries out," Folson said.
"We're totally reliant on the Lord God Almighty for the weather."
It looked "tough" for growers with the snow last week, Folson said.
But snow insulates the potatoes. When the snow melts, if temperatures remain cold, it could freeze potatoes.
When last week's snow melted, temperatures stayed above freezing, so Folson is hopeful that his potatoes are fine.
The resulting loss of crop would drive the prices the growers can charge up, but consumers wouldn't see much of a change at the grocery store.
"Growers will charge more, but there's a pretty big margin, so there's room for retailers to hold price," Kreis said.
Potatoes are a spot-market item, meaning their price changes from day-to-day. So it still is too early to tell for certain what will happen, Kreis said.
"We'll have to see, but I'm sure they won't get all of the potatoes out," he said.