PANAMA CITY, Fla. — Michael's leading edge careened onto northwest Florida's white-sand beaches as a still-growing Category 4 hurricane Wednesday, lashing the coast with tropical storm-force winds and rain and pushing a storm surge that could cause catastrophic damage well inland once it makes landfall.

The unexpected brute quickly sprang from a weekend tropical depression with top winds growing to 145 mph (230 kph), the most powerful hurricane in recorded history for this stretch of the Florida coast.

The sheriff in Panama City's Bay County issued a shelter-in-place order before dawn Wednesday, and Florida Gov. Rick Scott tweeted that for people in the hurricane's path, "the time to evacuate has come and gone ... SEEK REFUGE IMMEDIATELY."

At 8 a.m ., Michael's eye was about 90 miles (145 kilometers) from Panama City and Apalachicola, moving relatively fast at 13 mph (21 kph). Tropical-storm force winds extended 185 miles (295 kilometers) from the center, lashing the coast, and hurricane-force winds were coming closer, reaching 45 miles (75 kilometers) from the center.