If the temperatures near you are anywhere close to what they are here, i am thinking that corn will be in trouble. Here are a couple of charts showing the soil temps. If you look at the temps durning the after noon hours it might okay to plant, but look at the over night temps.
 One thing i noticed, over night the soil temps are lower than the air temp. Over the years i have found over night, normally the soil temps stays above the air temps in most case`s. These temps were taken in a field that still has frost.

(hovdes 4 21 2014 2 inch soil temp.bmp)

(hovdes 4 22 2014 2 inch soil temp.bmp)

hovdes 4 21 2014 2 inch soil temp.bmp (629KB - 50 downloads)

hovdes 4 22 2014 2 inch soil temp.bmp (573KB - 44 downloads)