Sunday has been gloomy and rainy, but Long Island has so far been spared from any thunderstorms.
That will change late this afternoon and through the evening, the National Weather Service says.
A severe thunderstorm watch is in effect for Nassau County until 10 p.m. Suffolk County is not under a watch, but a hazardous weather outlook remains in effect for the county.
The NWS says showers and thunderstorms could produce heavy rain with hourly rainfall rates of around an inch an hour.
If these heavier showers and thunderstorms move over the same locations, flash flooding of low-lying and poor drainage areas will be possible.
An isolated tornado cannot be ruled out in areas where severe weather occurs, the NWS says.
The rain will end by midnight in most areas.
The full forecast:
This Afternoon- Showers and thunderstorms. Some of the storms could produce heavy rainfall. High near 71. South wind around 15 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Tonight- Showers and thunderstorms, mainly before 1am. Some of the storms could produce heavy rainfall. Low around 68. South wind 10 to 17 mph. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.
Monday- Mostly sunny, with a high near 81. West wind 11 to 13 mph.
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