The National Weather Service is predicting a nor'easter will bring heavy rains Saturday and Sunday, which could lead to flooding.
A flood watch has been issued for Long Island, with 2 1/2 to 4 inches of rain expected, forecasters said. Higher amounts are likely locally.
"That would be problematic, especially with highly saturated ground from the snowmelt we've had recently that has elevated the water table," meteorologist Tim Morrin said.
Forecasters predict poor drainage and flooding across coastal areas. Basement flooding is expected.
The flood watch remains in effect from Saturday morning to Sunday morning.
Despite the gloomy forecast, the Bay Shore-Brightwaters St. Patrick's Day parade will go on as planned on Saturday, a parade official said Friday.
Other parade organizers said Thursday their events will also go on this weekend. Westhampton Beach, however, moved its parade to March 27.
Officials said light rain or drizzle on and off Friday will become steadier into Saturday, then could be heavy at times into Saturday evening.
To make matters worse, forecasters said sustained winds of 30 mph to 35 mph are also expected - with gusts up to 45 mph possible. In some areas, gusts could approach 60 mph.
"An increasing wind from the east to northeast - there's quite a strong pressure difference between a high over Québec, Canada, and this storm - is going to cause winds to increase," Tim Morrin of the National Weather Service in Upton said.
Moderate beach erosion is likely as well, forecasters said.
"There will be 24- to 36-hour duration of east to northeast winds and a lot of wave action on top of the tide, so erosion obviously will be a concern," Morrin said.
A gale is sustained winds of at least 35 mph.
"One thing we do have working for us is that the tides will not be astronomically high, but we do anticipate at least minor coastal flooding at times of high tide, especially in the back bays along the western portion of the South Shore, and definitely across the western Sound," Morrin said.
Lows in the mid- to upper 30s are expected, with highs in the mid-40s.
Heavy rain Saturday will taper off to light rain Sunday night into Monday, forecasters said, with sunny skies expected to finally return Tuesday.
With Nomaan Merchant