Anticipated to make landfall on Monday, Alberto is the first storm ahead of this year's Atlantic hurricane season, which formally starts on 1 June.

It will bring heavy rain and winds of 100kmh (65mph) across southern states, the US National Hurricane Center said.

It was centred about 185km (115 miles) south-west of Florida's Panama City, at 01:00 CET (6:00GMT).

Alberto had picked up strength as it headed north through the Gulf of Mexico, bringing with it the warning of life-threatening inundation, said the Miami-based hurricane centre.

It is forecast to drop as much as 30cm (12in) of rain across Mississippi to western Georgia and to bring storm swells of about 60-120cm (2-4ft) to low-lying areas.

Alberto comes during the Memorial Day weekend, and is expected to affect travel on Monday, when many people will return from their holidays.

It is the first named storm of the season, with 21 other names still to be used, including Beryl, Ernesto, Kirk, Nadine and Rafael.

Last year, a number of deadly hurricanes hit the US and Caribbean. Puerto Rico, for example, is still struggling with its recovery efforts following major infrastructure damage from Hurricane Maria in October.