Hurricane Michael strengthened to a category 2 storm with 160km/h winds on Tuesday as Florida’s governor warned it could bring "total devastation" to parts of the southern US state.

The storm – now located over the Gulf of Mexico – is sweeping towards the Florida coast at about 20km/h and is expected to make landfall on Wednesday, bringing with it "life threatening" storm surges and heavy rainfall, the National Hurricane Center said.

"It is a monstrous storm and the forecast [keeps] getting more dangerous," Florida governor Rick Scott said. "The time to prepare is now" he said, adding that it "poses a deadly threat and as it grows stronger, we can expect it to make landfall as a major category 3 storm".

He said it "could bring total devastation to parts of our state, especially in the panhandle."

A hurricane warning was up across the Florida panhandle, which is a low-lying area of beachfront resort and retirement communities on the northeastern Gulf coast.

Forecasters warned of coastal flooding with storm surge and tides projected to raise water levels by as much as 2.5m-3.6m in some areas.

Rainfall of 10cm-20cm, and as much as 30cm in isolated areas, "could lead to life-threatening flash floods," according to the National Hurricane Center, which warned that the storm’s approach could spawn tornados in northwestern Florida.

Michael was forecast to have the power to uproot trees, block roads and knock out power for days by the time it hits Florida on Wednesday. It is expected to weaken as it moves up into the southeastern US.

President Donald Trump, who was in Orlando delivering an address on Monday to a global association of police chiefs, said that the federal government was ready and urged residents to be prepared for the worst.

"Can you believe it? It looks like another big one," he said

The Carolinas are still recovering from Hurricane Florence, which left dozens of people dead and is estimated to have caused billions of dollars in damage last month.

It made landfall on the coast as a category 1 hurricane on September 14 and drenched some parts of the state with 100cm of rain.

Last year a string of catastrophic storms – including Irma, Maria and Hurricane Harvey – battered the western Atlantic, causing $125bn in damage when the Houston metropolitan area was flooded.

Scientists have long warned that global warming will make cyclones more destructive, and some say the evidence for this may already be visible.

At their most fearsome, these low-pressure weather fronts pack more power than the energy released by the atomic bomb that levelled Hiroshima.