What is a storm surge, and what is the threat from Hurricane Milton?

David Sampson and Danny Welker board up a house before the arrival of Hurricane Milton, in St Pete Beach, Florida, on Monday. Photograph: Octavio Jones/Reuters

Hurricane Milton has made landfall in Florida and millions of residents in the state have been told to evacuate.

Although the hurricane was downgraded to a strong category 3, forecasters said it would still make landfall as an “extremely dangerous major hurricane”. “No one in the area has ever experienced a hurricane this strong before,” the National Weather Service said.