By 8 a.m. Monday, Irma was about 105 miles north of Tampa, with sustained winds of 70 mph. A storm surge warning was discontinued from Flagler and Volusia counties south to Jupiter inlet, but a flash flood warning remains in effect for downtown Jacksonville.
"This is a particularly dangerous situation," a National Weather Service alert warned. "Water is expected to rise another 1 to 2 feet when winds switch to the south and push water northward into downtown — and the high tide begins to come into the river. Move to higher ground now. This is an extremely dangerous and life-threatening situation."
Hurricane warnings in north and central Florida were downgraded to tropical storm warnings.
"Irma is continuing to weaken as it moves across the western Florida peninsula, with the eye dissipating and weakening banding near the center," the National Hurricane Center (NHC) said in its 8 a.m. forecast. "Life-threatening storm surge" is a danger along portions of the coasts of Florida, Georgia and South Carolina, the NHC said.
Irma's heavy rain could also bring flash flooding and rapid rises on creeks, streams and rivers. Forecasters said significant river flooding was likely over the next five days in Florida and southern Georgia.
Irma made landfall at Cudjoe Key just after 9 a.m. Sunday as a Category 4 storm before weakening as it spun up the Florida peninsula. Gov. Rick Scott requested a major disaster declaration from President Donald Trump "to help bring important federal resources and aid to Florida" once Irma passes, he said. Trump approved it.
The storm made its second landfall at Marco Island as a Category 2 storm at 3:30 p.m. Sunday, before heading north to Naples across the bay. Even before Hurricane Irma landed in Naples, the National Hurricane Center — expecting more than a dozen inches of rain and a storm surge as high as 15 feet — issued a flash flood warning.
"Along with the high wind threat, another concern will be the potential for life-threatening storm surge inundation along and near the Southwest Florida Gulf Coast as the storm exits," the weather service warned West Central Florida.
For a time, the mainland was cut off from the tourist mecca of Sanibel Island, known for its beaches and seashells that wash ashore from the Gulf of Mexico.
Lee County said state and local Department of Transportation inspectors would check out the causeways to the coastal islands early Monday — and warned that "due to Hurricane Irma's significant wave action, the Sanibel Causeway may have been impacted." Meantime Sanibel police were restricting traffic across the causeway.
Tornado watches disappeared for central and eastern portions of Florida. But the weather service reminded residents of Florida's eastern coast that "life-threatening surf and rip current conditions" were likely byproducts of Irma.
In Miami-Dade, the highest gust Sunday was 99 miles per hour, said Ed Rappaport, acting director of the National Hurricane Center. Monday offered a mixed forecast for Miami-Dade County — gusts of winds of up to 50 miles per hour in the early morning hours, with a sunny upper 80s temperature day predicted and the possibility of showers and thunderstorms.
"Due to its recent more inland push, Irma's center is now forecast to remain over Florida and then move over the southeastern United States for the duration of its existence," the weather service said, predicting it would become a tropical depression over Mississippi by Tuesday afternoon and adding that it should dissipate over Tennessee on Wednesday.
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