The Arctic blast most the Midwest is feeling this week has raised concerns about how badly the plunging temperatures will damage the winter wheat crop.

Don Keeney, agricultural meteorologist of MDA Weather Services told the Associated Press that he expected about a third of the country’s winter wheat acres will be affected by this week’s severe temperatures.

He explained that some freeze damage was expected on Wednesday, but with colder air moving into the Midwest for Thursday, the bulk of the damage was expected to occur Thursday morning.

Subzero temperatures are expected across much of the central Plains states Thursday morning including the states of eastern Nebraska, southwestern Iowa, northern and eastern Missouri, south-central Illinois, southern Indiana and southern Ohio, according to MDA Weather Services. The majority of wheat fields in this area does not have any snow covering to insulate them and damage is expected. Keeney said most of Kansas is expected to be spared significant damage from the frigid air.

Earlier this season, winter wheat deteriorated in many states, especially Illinois where USDA rated only 24 percent of the wheat crop as good to excellent as of Jan. 4.