After a hard freeze, there could be questions regarding prussic acid in sorghum. Prussic acid poisoning is more of a concern when grazing sorghum than when harvested for hay or silage.
After a cold March, April started out warm in Kansas. This report discusses the likelihood of varying thresholds of freezing temperatures in Kansas after April 1. The impact of low temperatures on newly emerged crops will vary depending on how low the temperature drops, the duration of the low temperatures, and other factors.