Picture shown is for illustrative purposes only.

Tropical Storm Arthur formed off the coast of Florida on Saturday, making it the sixth straight year for a named storm to develop before the official June 1 start of the Atlantic hurricane season.

As of 2am on Sunday, the storm’s center was located about 405 miles (650 kilometers) south-southwest of Cape Hatteras, North Carolina, the US National Hurricane Center in Miami said. Arthur has top sustained winds of 40 mph (65 kph) and is moving to the north-northeast at 13 mph (20 kph), officials said.

READ MORE

New Orleans threatened by floods as big storm forms

Idai storm kills at least 360 in southern Africa

A tropical storm watch remained in effect for parts of the North Carolina coast. Forecasts say Arthur will stay well offshore of Florida, Georgia and South Carolina on Sunday and then approach the North Carolina coast on Monday, where it will drop between 1 and 2 inches of rain Sunday night and Monday.

Dangerous coastal surf conditions and rip currents are expected to spread northward from Florida to the mid-Atlantic states during the next few days.

While there may be a component of warming waters and climate change in other pre-June storms, Arthur is more of a subtropical storm system than a traditional named storm and its water is cooler than what’s usually needed for storm formation, said Colorado State University hurricane researcher Phil Klotzbach.