The threat of Hurricane Milton to Florida’s densely populated Tampa Bay region led to one of the largest evacuations in the state’s history this week. Officials urged millions of people out of possible harm’s way.

The evacuations started on Monday, slowing highways to a crawl, and grew in number on Tuesday, with officials warning there was no time to lose. Milton is expected to strike the vulnerable Tampa region late Wednesday or early Thursday. The area hasn’t had a direct strike from a hurricane in more than a century.

Some 5.5 million people live in areas that were under mandatory or voluntary evacuation orders as of Tuesday morning, according to the Federal Emergency Management Agency. And more orders were issued by local and state officials throughout the day, expanding the evacuation zone.

To try to keep major evacuation routes from clogging, officials urged residents to go to nearby shelters and not travel farther inland than necessary. Still, roads saw 150 percent of normal traffic on Monday, according to state officials.

Tolls were waived and highway shoulders were opened to try to keep cars moving, but traffic still slowed to 20 miles per hour in some spots. It eventually cleared by 1 a.m. on Tuesday, state officials said, though more jammed highways were expected later in the day as evacuation orders grew.

Gov. Ron DeSantis of Florida encouraged people to leave using state roads, too.