The weather outlook in Georgetown includes no air temperatures (currently) in the 30s through April 21st. With that outlook, soybean and corn planting can probably start late next week. Although there can still be a random late freeze, the probability really drops after April 15th in our region.
The preferred soil temperature for corn germination is 50°F, which allows the seed to begin root and shoot growth. Many of the weather stations on DEOS (http://www.deos.udel.edu/) have soil temperature as an option, so you can track current conditions. Since April 1st, soil temperatures have ranged from 47-53°F in Newark and 47-55°F in Georgetown. Soil temperature does not change as rapidly as air temperature, so we would expect the daytime temperatures over the next week to keep soils above 50°F, even when nighttime temperatures dip into the 40s.
Figure 1: Corn on the left was planted in bare plots while corn a few inches away in a rye cover crop appears unaffected.