Hurricane Irma, which has toppled cranes, swallowed streets and left millions without power, weakened to a Category 1 storm Monday but remained dangerous as it continued its furious climb up Florida's southwest coast.

Warnings of hazardous storm surges remained in effect through vast swaths of peninsular Florida, where more than six million people had been ordered to flee Irma's path -- one of the biggest evacuations in US history.

"As little as six inches of moving water can knock you down," tweeted the state's governor Rick Scott following the downgrade.

"Stay inside. Stay safe," he added.

Maximum sustained winds had decreased to 85 miles per hour as of 2:00 am local time (0600 GMT), with Irma projected to become a tropical storm as it moved into northern Florida or southern Georgia later Monday.

After wreaking a trail of death and destruction through the Caribbean, Irma had killed three people when it struck the southern Florida Keys island chain as a more powerful Category Four on Sunday.

More than four million customers were without power throughout the state, according to Florida's Division of Emergency Management. Florida Power and Light said it had "safely shut down" one of two nuclear reactors at its Turkey Point power plant.

Source: Khaleej Times