MIAMI (BLOOMBERG) - Heavy rains are threatening to topple a century-old record in Miami even if the storm that brought them does not have a name.

The system, dubbed "a potential tropical cyclone" by the National Hurricane Centre, swept in from the Gulf of Mexico and is wringing itself out across south Florida on its way towards the Atlantic later on Saturday (June 4).

Forecasters had thought it would become Tropical Storm Alex, but larger weather patterns have torn at its structure, the centre said.

"In other words, the system has gone the wrong way in becoming a tropical cyclone," Mr Robbie Berg, a senior hurricane specialist with the agency, wrote in a forecast.

The rains have left Miami streets awash as upwards of 11 inches (28cm) of rain have fallen in some areas since Friday, with the prospect of more through the day, said Ms Ana Torres-Vazquez, a National Weather Service meteorologist.

Although most of south Florida has been battered with rainfalls, the highest totals have accrued in Miami-Dade County. Tallies are still being collated, but it is more than likely Saturday's storm total will break the record for June, which stands at 8.25 inches from 1901.

The City of Miami Fire Rescue agency urged residents early on Saturday morning to avoid driving, indicating on Twitter that they were already responding to people trapped in vehicles. Several drivers had to be rescued from flooded cars, according to the Miami Fire Rescue's Facebook feed.

On Twitter, the City of Miami-Fire Rescue agency urged residents early on Saturday morning to avoid driving entirely. Some city streets are completely inundated.

About one-third of the 515 flights cancelled across the United States in the last 24 hours were from Florida airports including Miami and Fort Lauderdale, said FlightAware, an airline tracking company.

It is possible some areas of southern Florida could get as much as 15 inches of rain by the time the storm leaves, said Mr Bob Oravec, a senior branch forecaster with the US Weather Prediction Centre.

After the system crosses Florida, there is still a chance it could become the Atlantic's first named storm of the six-month hurricane season, which began on Wednesday. It is forecast to drift east across the Atlantic passing just north of Bermuda by Monday.