How big is Hurricane Milton and how much damage can a Category 4 storm cause?

More than a million people have been ordered to evacuate as a potentially "catastrophic" Hurricane Milton bears down on the US, bringing wind speeds of up to 155mph.

Milton became the third-fastest intensifying storm on record in the Atlantic Ocean, growing from a tropical storm to a Category 5 hurricane in just 24 hours.

Forecasters have warned of a storm surge of up to 15 feet, the highest ever in the region.

Tampa Bay Mayor Jane Castor told CNN residents should get out of the evacuation zones, saying a 10-12ft surge would be disastrous. "There’s never been one like this," she said. "This is literally catastrophic. I can say without any dramatisation whatsoever if you choose to stay in one of those evacuation areas, you’re gonna die."

Castor added: "This is something I never seen in my life. People need to get out. If we have that predicted storm surge, it is not survivable."

What is a Category 4 hurricane?

A Category 4 hurricane is the second-most dangerous classification on the Saffir-Simpson Hurricane Wind Scale, which goes from one to five.

Category 4 hurricanes have sustained winds of 130-156 mph, and are projected to cause 'catastrophic' damage.

The US National Weather Service describes the effects of a Category 4 hurricane as likely to include:

• Well-built framed homes can sustain severe damage with the loss of most of the roof structure and/or some exterior walls

• Most trees will be snapped or uprooted and power poles downed.

• Fallen trees and power poles will isolate residential areas.

• Power outages will last weeks to possibly months.

• Most of the area will be uninhabitable for weeks or months.

What are the warnings around Hurricane Milton?

Hurricane Milton was downgraded to a Category 4 hurricane as it has drawn closer to the US, with maximum wind speeds of 155mph, but remains extremely dangerous, according to the US National Hurricane Center.

The International Space Station posted a video showing Milton moving across the Gulf of Mexico.

The path of the storm is also unusual - it is exceedingly rare for a hurricane to form in the western Gulf, track eastward, and make landfall on the western coast of Florida. Gulf hurricanes typically form in the Caribbean Sea and make landfall after travelling west and turning north.

Jamie Rhome, deputy director of the National Hurricane Center, has also warned that Milton was expected to grow in size before making landfall on Wednesday.

The Hurricane Center has forecast storm surges of 10 to 15 feet along a stretch of coastline north and south of Tampa Bay, a city which hasn't had a direct hit from a hurricane in more than a century. This will put hundreds of miles of coastline within the storm surge danger zone.

Milton is likely to remain a hurricane for its entire journey across the Florida peninsula (rather than being downgraded to a tropical storm).

The US National Hurricane Center projected the storm was likely to hit near the densely populated Tampa Bay metropolitan area, home to more than 3 million people, after first impacting Mexico’s Yucatan Peninsula.

Florida is still suffering the effects of the devastating Hurricane Helene less than two weeks ago.

Counties have ordered evacuations and advised people to move to high ground, with local officials warning of traffic jams and long lines at petrol stations.

When were previous Category 4 hurricanes?

Between 2000 and 2024, 38 Category 4 hurricanes formed in the Atlantic Ocean.

The recent Hurricane Helene made landfall in Florida as a Category 4 hurricane, as did Hurricane Ida in 2021 in Louisiana and Hurricane Laura in 2020. Hurricane Harvey hit Texas in 2017 as a Category 4 hurricane.

For context, Hurricane Katrina in 2005 - one of the most notable disasters in recent US history - was a Category 1 hurricane when it hit Florida on 25 August.

It then intensified into a Category 5 hurricane as it tracked over the Gulf of Mexico. When it hit Louisiana four days later it had been labelled a Category 3, with recorded wind speeds of 140 miles per hour. The hurricane then tracked east with catastrophic consequences in Alabama and Mississippi.

It is believed 1,833 people died and millions were left homeless in the hurricane and the flooding that followed, with Katrina causing approximately $161 billion in damage.

Why are hurricanes named?

Weather authorities in the US name hurricanes to make it easier to communicate, particularly when there are multiple tropical storms active.

The National Hurricane Center says: "In the past, confusion and false rumours have arisen when storm advisories broadcast from radio stations were mistaken for warnings concerning an entirely different storm located hundreds of miles away."

Previously, local people had named hurricanes after Saint's days, based on the date these occurred.

The United States started naming storms after women in 1953 and added male names in 1978.