The National Weather Service is warning people in southeastern St. Lawrence County of flooding due to the heavy rain this morning.

A flash flood warning is issued when a flash flood is imminent or occurring in the area. A flash flood is a sudden, violent flood after a heavy rain. New York State Police in Gouverneur and the St. Lawrence County Sheriff’s office say their patrols have not seen any flooding of note so far.

The warning, posted at 7:44 a.m., is set to expire at 11:45 a.m.

Some locations that will experience flooding, the NWS says, include Cranberry Lake, Horseshoe Lake, Star Lake, Oswegatchie, Fine, Pitcairn, Wanakena, Aldrich, Newton Falls, South Edwards, Lower Oswegatchie and Sabattis.

At the time of the posting, radar showed showers, thunderstorms and heavy rain across the warning area.

If you find yourself in a flooded area, the NWS warns people to move to higher ground immediately. “Act quickly to protect your life. Turn around. Don’t drown when encountering flooded roads. Most flood deaths occur in vehicles,” the NWS warning says.

At 9 a.m., radar indicated that the heaviest rain had moved past the area, but that more rain is likely on the way. Flooding could take time to develop, so the danger is not past.

For the rest of St. Lawrence County, thunderstorms are likely today. High temperatures will be around 75. It will be breezy, with 21 to 25 mph winds and gusts approaching 40 mph.

Tonight skies will be partly cloudy with lows in the low 50s. Winds will diminish to light and variable tonight.

Wednesday, the day will begin under sunny skies but clouding up with a possibility of showers in the afternoon. Highs will be in the low 70s.

The NWS forecast for the St. Lawrence Valley and northwestern Adirondacks:

Today: Showers likely and possibly a thunderstorm before 11am, then a chance of showers and thunderstorms, mainly between 11am and 5pm. Some of the storms could produce small hail, gusty winds, and heavy rain. Mostly cloudy, with a high near 78. Breezy, with a southwest wind 21 to 25 mph, with gusts as high as 38 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Partly cloudy, with a low around 53. West wind 12 to 17 mph becoming light and variable after midnight.

Wednesday: A 20 percent chance of showers after 3pm. Sunny, with a high near 72. Light west wind increasing to 12 to 17 mph in the morning.

Wednesday Night: A 50 percent chance of showers before 1am. Partly cloudy, with a low around 53. Southwest wind 7 to 14 mph. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Sunny, with a high near 72. Light west wind increasing to 6 to 11 mph in the morning.

Thursday Night: Partly cloudy, with a low around 54. North wind 5 to 7 mph becoming calm in the evening.

Friday: Mostly sunny, with a high near 75. Northeast wind 3 to 7 mph.

Friday Night: Partly cloudy, with a low around 54. Northeast wind around 6 mph becoming calm in the evening.

Saturday: Mostly sunny, with a high near 76. Calm wind becoming east around 5 mph in the afternoon.

Saturday Night: Mostly cloudy, with a low around 58. East wind around 6 mph.

Sunday: A 30 percent chance of showers. Partly sunny, with a high near 72. Southeast wind 5 to 7 mph.

Sunday Night: A 30 percent chance of showers. Mostly cloudy, with a low around 57. East wind around 7 mph.

Monday: A 30 percent chance of showers. Partly sunny, with a high near 73. Southeast wind around 5 mph becoming calm in the morning.