Officials in Miami Beach on Sunday said they will not allow people to enter the city until Tuesday at noon, The Miami Herald reported.
The city will reportedly be barricaded.
Irma weakened to a Category 1 storm as the massive hurricane zeroed in on the Tampa Bay region early Monday after hammering much of Florida with roof-ripping winds, gushing floodwaters and widespread power outages.
The hurricane's maximum sustained winds weakened to 85 mph with additional weakening expected.
As of 2 a.m. EDT, the storm was centered about 25 miles northeast of Tampa and moving north-northwest near 15 mph.
Irma continues its slog north along Florida's western coast having blazed a path of unknown destruction. With communication cut to some of the Florida Keys, where Irma made landfall Sunday, and rough conditions persisting across the peninsula, many are holding their breath for what daylight might reveal.