The National Hurricane Center is not mincing words:

...LIFE-THREATENING STORM SURGE, CATASTROPHIC WINDS AND FLOODING EXPECTED IN THE FLORIDA PENINSULA...

Key Messages: 1. Life-threatening storm surge is increasingly likely along the Florida west coast where a storm surge warning is in effect, with the highest risk from Naples to the Sarasota region. Residents in these areas should listen to advice given by local officials and follow any evacuation orders for your area.

2. Hurricane-force winds are expected in the hurricane warning area in southwest and west-central Florida beginning Wednesday morning with tropical storm conditions expected overnight.  Devastating wind damage is expected near the core of Ian. Residents should rush all preparations to completion.

3. Heavy rainfall will affect most of the Florida Peninsula for the next several days, spreading to the rest of the Southeast U.S. by Thursday and Friday, likely causing flash, urban, and small stream flooding. Considerable flooding is expected with widespread, prolonged moderate to major river flooding expected across central Florida. 
 

Predicted storm-force wind arrival times
[Photo Credit: NOAA/NHC] Predicted storm-force wind arrival times
Predicted hurricane path
[Photo Credit: NOAA/NHC] Predicted hurricane path