The National Weather Service has St. Lawrence County under a hazardous weather warning through 7 p.m. Tuesday as a system carrying days' worth of snow and ice rolls in.

The NWS says there is a 100 percent chance of snow Monday night and Tuesday morning, which on Tuesday will change to sleet and wintry mix, the NWS says. 

Snow is expected to pile a minimum of four inches across the county by Wednesday. Massena could see up to 10 inches.

Temperatures are predicted to go from the low teens Monday night to the mid 30s Tuesday.

Tuesday night brings up to a 50 percent chance of freezing drizzle, the NWS says, with temperatures in the high 20s.

Wednesday brings a 30 percent chance of snow and drizzle, with 50 percent odds of snow at night. Temperatures are forecast to go from the high 30s during the day to the low 30s at night.

The detailed forecast for Potsdam:

Monday night - Snow, mainly after 11 p.m. The snow could be heavy at times. Temperature falling to near 16 by 8 p.m., then rising to around 24 during the remainder of the night. East wind 9 to 11 mph. Chance of precipitation is 90 percent. Total nighttime snow accumulation of 3 to 5 inches possible.

Tuesday - Rain and sleet before 4 p.m., then drizzle likely between 4 and 5 p.m., then freezing drizzle likely after 5 p.m. High near 33. East wind 5 to 10 mph. Chance of precipitation is 100 percent. Little or no ice accumulation expected. New sleet accumulation of 1 to 2 inches possible.

Tuesday night - Freezing drizzle likely before 8 p.m., then a chance of drizzle between 8 p.m. and 9 p.m., then a chance of freezing drizzle after 9 p.m. Cloudy, with a low around 29. Light and variable wind.

Wednesday - A chance of drizzle or freezing drizzle before 1pm, then a chance of rain and sleet between 1pm and 2pm, then a chance of drizzle after 2pm. Mostly cloudy, with a high near 36. Light southwest wind. Chance of precipitation is 30%. Little or no sleet accumulation expected.

Wednesday night - A 50 percent chance of snow showers. Cloudy, with a low around 30. Southwest wind 3 to 6 mph. New snow accumulation of less than one inch possible.

Thursday - A 40 percent chance of snow showers. Mostly cloudy, with a high near 35. West wind 6 to 9 mph.

Thursday night - A 40 percent chance of snow showers. Mostly cloudy, with a low around 25. West wind around 9 mph.

New Year's Day - A 30 percent chance of snow showers. Cloudy, with a high near 31. West wind 7 to 14 mph.

Friday night - A 40 percent chance of snow showers. Mostly cloudy, with a low around 17. West wind 8 to 11 mph.

Saturday - Partly sunny, with a high near 22. West wind around 9 mph.

Saturday night - A 30 percent chance of snow showers. Mostly cloudy, with a low around 11. West wind 5 to 9 mph becoming light.

Sunday - Mostly cloudy, with a high near 23. Northwest wind around 6 mph.

Sunday night - Mostly cloudy, with a low around 11. Northwest wind around 6 mph becoming calm in the evening.

Monday - Partly sunny, with a high near 27. West wind 5 to 8 mph.