Florida Gov. Rick Scott has declared a State of Emergency for all 67 counties in the state.

"Hurricane Irma is a major and life-threatening storm and Florida must be prepared," Scott said. "I have continued to be briefed by the Florida Division of Emergency Management on Hurricane Irma and current forecast models have Florida in Irma's path – potentially impacting millions of Floridians."

Irma is packing winds in excess of 130 mph as it heads for key islands in the Caribbean.

Earlier Monday, Irma was a Category 3 but was upgraded to a Category 4 during the National Hurricane Center's 5 p.m. advisory.

Changes in the storm's structure will cause fluctuations in the intensity of the storm.

Hurricane research planes have been flying through and around Irma since Sunday gathering data and information about the structure and intensity of the storm, as well as hopefully add to some consistency and accuracy in model forecasts assuming better analysis/input for the models.

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