The Morse code for this episode means "PRAY FOR NYC"
In this episode the survivors get some information about which places were nuked around them, and Lawrence, Kansas is mentioned. One of the sheriff's deputies even asks how come Lawrence was hit and Topeka was not. Lawrence, Kansas is the small town where the events of the 1982 television drama "The Day After" are taking place. It's apparently a nod to the mother of all nuclear holocaust movies.
In the scene where Johnston Green is cooling his thermometer in a glass of water, he says that he "doesn't want to be the reason this town runs out of antibiotics". Earlier in the series it is stated that he has the flu. Influenza is a virus, and thus he would not be given antibiotics as they would have no effect.
Johnston Green's thermometer is a rectal thermometer.