good evening from south florida tonight. right here along u.s. 1, the entrance to the florida keys, where they are not allowing any families to return home. state police road blocks just ahead here amid reports of devastation in the keys. two search and rescue mobile units just passed by us, their sirens on. they were headed into the keys. in a moment here, we will head to amy robach who flew into the storm zone. what she witnessed on the ground herself. but the other part of this story unfolding right now, the storm slamming into other american cities tonight. a dangerous storm surge in jacksonville, florida. and it is hammering georgia tonight, on its way to atlanta. reports parts of charleston are under water, too. irma is a powerful tropical storm now, stretching 400 miles across. so, we begin with abc's linsey davis on the urgent water rescues. she's in jacksonville, leading us off tonight. >> reporter: tonight, irma pushing northward. in jacksonville, massive storm