Seas off the southern coast of Long Island were running at 3 to 4 feet Monday, but could kick up to 4 to 6 feet by Tuesday afternoon if threatened thunderstorms move in.

A high pressure system was building Monday and a cold front was expected to approach Tuesday and pass through the area Tuesday night, causing a low pressure system to impact the waters, according to the National Weather Service.

On the Long Island Sound, seas were expected to about 1 foot Monday and around 2 feet Tuesday afternoon, forecaster said.

advertisement | advertise on newsday

There is a hazardous weather outlook for the region for Tuesday because of the possibility of thunderstorms, but there were no small craft advisories for area waters Monday morning.

The cold front could produce strong winds Tuesday, possibly up to 35 knots, according to Jim Connolly, a meteorologist at the National Weather Service in Upton.