All of St. Lawrence County is under a two-day hazardous weather outlook with a chance at "localized flooding," the National Weather Service says.

They say showers and thunderstoms today could cause rising waters. They call for a 20 percent chance of heavy rain today before 2 p.m. in all St. Lawrence County communities. That is expected to give way to a partly sunny day in Ogdensburg.

Temperatures are predicted in the low- to mid-80s.

Tonight's forecast is for partly cloudy with temperatures around 65 degrees.

Sunday's forecast calls for 70 to 80 percent odds of heavy rain. That could be accompanied by a heat index in the 90s. Actual temperatures are once again predicted in the low- to mid-80s.

Sunday night brings 80 to 90 percent odds of heavy rain with thermometers dropping to the low-60s.

Monday is predicted to bring a 30 percent chance of storms, giving way to a partly sunny remainder of the day and temperatures around 80.

The detailed forecast for Potsdam:

Today - A 20 percent chance of showers and thunderstorms before noon. Some of the storms could produce gusty winds and heavy rain. Partly sunny, with a high near 86. West wind 6 to 9 mph.

Tonight - Partly cloudy, with a low around 65. Southwest wind 3 to 6 mph.

Sunday - Showers and thunderstorms likely, mainly after 2pm. Some of the storms could produce heavy rain. Partly sunny, with a high near 86. Heat index values as high as 93. South wind 5 to 14 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Sunday night - Occasional showers and thunderstorms, mainly before 1am. Some of the storms could produce heavy rain. Low around 63. Southwest wind 5 to 8 mph. Chance of precipitation is 80%. New rainfall amounts between a quarter and half of an inch possible.

Monday - Sunny, with a high near 82. Southwest wind 6 to 11 mph.

Monday night - Partly cloudy, with a low around 64. Southwest wind 6 to 8 mph.

Tuesday - A 30 percent chance of showers after 8am. Partly sunny, with a high near 81. Southwest wind 7 to 11 mph.

Tuesday night - Partly cloudy, with a low around 62. West wind 3 to 8 mph.

Wednesday - Mostly sunny, with a high near 81. Light west wind increasing to 5 to 9 mph in the morning.

Wednesday night - Partly cloudy, with a low around 59. West wind around 6 mph becoming calm in the evening.

Thursday - Mostly sunny, with a high near 81. Calm wind becoming west 5 to 8 mph in the morning.

Thursday night - Partly cloudy, with a low around 59. Southwest wind 5 to 7 mph.

Friday - Mostly sunny, with a high near 81. West wind 5 to 9 mph