2012 I had put some in early for our area.  April 25th.  We got a cold rain and I had one variety not come up.  It was probably 65% germ.  I had 4 varieties on that 80 and that was the only one I had an issue with with the rest at 95%+.

I understand there is "too cold" but I think seed quality, planting depth, soil texture and possible rain events following play a larger role.  What caused the other 3 varieties to thrive while the one variety failed?  Most likely seed quality and or genetic traits.

FWIW, the variety that didn't come up well still yielded "ok" at roughly 10 bpa less. Even though the population was down significantly it seemed to flex ok.  It did show the characteristic cold imbibition such as corkscrewing and leafing out before it emerged.  The planting depth was 1.75" and there was no crust.

http://www.agry.purdue.edu/ext/corn/news/timeless/Corkscrews.html

For that reason, I waited this spring.  After it finally dries up, it will be go time.