Frost has been a concern of farmers for quite awhile because of the late maturing corn and soybean crops. Delayed planting in the spring due to wet weather has pushed development of crops about two weeks behind schedule. On Tuesday, several cities in the Upper Midwest reported temperatures of 34.

"We continue to just barely avoid what would be a damaging freeze across these areas where we see so many immature crops at this point," says USDA meteorologist Brad Rippey.

Rippey says that six states in those areas still have only a third to a half of the corn mature. Although frost can be expected soon, the forecast says a hard freeze will likely be several weeks away.