The National Weather Service has issued a flash flood watch for Northeast and Southeast Suffolk overnight and through Thursday morning.
"Multiple waves of low pressure along a frontal boundary just offshore will produce rounds of showers and a few thunderstorms across the watch area. Rainfall amounts of 1 to 3 inches with locally up to 4 inches are possible. There is some uncertainty where the axis of heaviest rainfall will set up," the weather service said in an online statement.
There is also a high risk of rip currents off South Nassau beaches all day Thursday, the weather service said.
The rain is forecast to fall in Suffolk between 10 p.m. and 4 a.m., returning again possibly Thursday morning. Showers are still possible Wednesday overnight for Western Long Island but the chance is about 50%.
Thursday afternoon, Friday and Saturday should feature sunny skies and daytime temperatures in the high 70s. The only chance of rain right now is for Saturday night, the weather service said.