A batch of storms will develop over the lower Hudson Valley late Wednesday afternoon and then move southeast, toward southern Connecticut and Long Island Sound, said Tim Morrin, a meteorologist with the Upton-based service.
By the time the rain hits the North Shore, Morrin said, the storms most likely will be played out.
"We're confident when that line of storms reaches Long Island they will be weakening," Morrin said. "There may be showers and maybe an isolated thunderstorm, but it will be later."
Once the rain passes, the temperatures should reach the mid-80s and leave clear, sunny skies from Thursday through early in the evening on Sunday, the service said.
Overall, the chance for precipitation Wednesday is 30 percent, with rainfall amounts up to one-10th of an inch.
There is a small chance thunderstorms developing Wednesday, between 2 p.m. and 6 p.m., with gusty winds and hail for isolated parts of Long Island Sound, east and west of New Haven, Conn., and Port Jefferson, the service said in a hazardous weather outlook.