Hot and humid weather is expected today as high pressure moves in from east of St. Lawrence County, but rain could reach us tonight and Tuesday.

Highs today will reach about 90 degrees, according to the National Weather Service.

Dewpoints will climb to the low to mid 60s today, lifting heat indices to the mid 90s for an hour or two in the Saint Lawrence Valley.

Lows tonight will be quite warm, in the low 70s, and dewpoints will climb through the night in the Saint Lawrence Valley, so it will feel fairly humid and uncomfortable for sleeping.

A cold front will approach from the west tonight and push through the North Country Tuesday evening.

Along and ahead of the front, showers and a few thunderstorms will develop tonight and become more widespread Tuesday. A few stronger storms are possible, containing heavy rainfall and dangerous cloud to ground lightning.

Once the front exits to the east Tuesday evening, surface high pressure will keep the area mainly dry through Friday.

Unsettled weather returns for the weekend as the upper-level ridge overhead breaks down.

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

• Today: Mostly sunny and hot, with a high near 91. Southwest wind 3 to 7 mph.

• Tonight: A chance of showers and thunderstorms, then showers likely and possibly a thunderstorm after 2am. Mostly cloudy, with a low around 70. South wind around 7 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

• Tuesday: Showers and thunderstorms likely, mainly before 1pm. Some of the storms could produce heavy rain. Cloudy, then gradually becoming mostly sunny, with a high near 82. Southwest wind around 8 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.

• Tuesday Night: A 30 percent chance of showers before 7pm. Partly cloudy, with a low around 53. Northwest wind 6 to 8 mph. New precipitation amounts of less than a tenth of an inch possible.

• Wednesday: Sunny, with a high near 76. Northwest wind 6 to 8 mph.

• Wednesday Night: Clear, with a low around 51. Northwest wind around 5 mph becoming calm in the evening.

• Thursday: Sunny, with a high near 83. Southwest wind 3 to 6 mph.

• Thursday Night: Mostly clear, with a low around 58. South wind 3 to 5 mph.

• Friday: Mostly sunny, with a high near 87. South wind around 6 mph.

• Friday Night: Partly cloudy, with a low around 63. South wind 3 to 6 mph.

• Saturday: A 30 percent chance of showers. Partly sunny, with a high near 86. Southeast wind around 6 mph.

• Saturday Night: A 40 percent chance of showers. Mostly cloudy, with a low around 63. Southeast wind around 6 mph.

• Sunday: A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a high near 82. Southeast wind around 7 mph.