Florida Gov. Rick Scott on Thursday urged residents along both coasts to heed evacuation orders as Hurricane Irma approached — noting ominously that “this thing is bigger than our entire state.”

While forecasts showed the center of the Category 5 storm nearing the eastern coast, the so-called “cone of uncertainty” — which shows where it could strike — covered all of the Sunshine State.

“So take this seriously. Leave now, don’t wait,” he warned during a morning briefing. “It’s wider than our entire state and could cause major and life-threatening impacts on both coasts.”

Scott announced that he activated an additional 3,000 members of the Florida Army and Air National Guards to prepare for the storm’s potential impact.

A total of 4,000 members have now been activated and 3,000 additional National Guard members will be activated Friday, when the entire force will be deployed, he said.

“These men and women are putting themselves in harm’s way to save the lives of their fellow Floridians while many of their own families are evacuating,” Scott said. “I am proud of their commitment to keeping our families safe.”

The governor said 6,800 people had volunteered in the past 24 hours, but stressed that the state needed a total of 17,000 to handle a possible disaster.

Scott also issued a stark reminder about Irma’s ferocity.

“Remember, Hurricane Andrew is one of the worst storms in the history of Florida. This is much worse and more devastating on its current path,” he said about the 1992 ‘cane.

At least 25,000 people so far have left the Keys after all visitors were ordered to clear out, causing bumper-to-bumper traffic on the single highway that links the chain of low-lying islands to the mainland.

Mayors in Miami-Dade and Broward counties issued mandatory evacuation orders starting Thursday morning for barrier islands and low-lying areas in the metro area of 6 million, where forecasters predicted the hurricane with winds of 180 mph could strike by early Sunday.

Scott also has declared a state of emergency and asked the governors of Alabama and Georgia to waive trucking regulations so tankers can ferry fuel into Florida quickly.

Brevard County also just announced a mandatory evacuation order, starting at 3 p.m. Friday for Merritt Island and low-lying areas on the India River Lagoon.

Mandatory evacuation orders were issued for visitors in Monroe County as of Thursday morning and for residents as of Thursday night.

And voluntary orders were issued Thursday for Collier Count and Marco Island.