By our calculations, you should look at sowing Ambrosia about 14 days after your last frost date.
A sugar-enhanced, mid-season, bi-color classic hybrid.
Open-pollinated versions of this are also available.
Released in 1989 by Breeder and vendor Crookham. 1
1 http://cuke.hort.ncsu.edu/cucurbit/wehner/vegcult/sweetcornal.html