A high pressure system will keep warm temperatures and mostly dry conditions over the St. Lawrence Valley through Monday night with chances of showers and thunderstorms increasing on Tuesday from an approaching low pressure system, according to the National Weather Service.

The chance of showers and thunderstorms is expected linger through the end of the week along with cooler temperatures.

The rest of today will be sunny with highs in the mid 80s with light and variable winds, TWS says.

Lows will reach around upper 50s overnight with Monday's forecast seeing partly cloudy skies and highs in the mid 80s.

The forecast for the rest of the week is as follows:

Monday Night Partly cloudy, with a low around 60. Calm wind becoming south 5 to 7 mph after midnight.

Tuesday Showers likely and possibly a thunderstorm, mainly after 2pm. Increasing clouds, with a high near 76. South wind 7 to 11 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.

Tuesday Night Showers likely and possibly a thunderstorm, then occasional showers after 8pm. Low around 63. Southeast wind around 10 mph. Chance of precipitation is 80%. New rainfall amounts between a half and three quarters of an inch possible.

Wednesday Rain. High near 70. South wind 6 to 8 mph. Chance of precipitation is 80%.

Wednesday Night Rain likely. Mostly cloudy, with a low around 56. Light southwest wind. Chance of precipitation is 60%.

Thursday Showers likely. Mostly cloudy, with a high near 65. West wind 5 to 7 mph. Chance of precipitation is 60%.

Thursday Night A 50 percent chance of showers. Mostly cloudy, with a low around 53. West wind around 7 mph.

Friday A 50 percent chance of showers. Mostly cloudy, with a high near 68. West wind 6 to 9 mph.

Friday Night A 30 percent chance of showers. Mostly cloudy, with a low around 55. Southwest wind around 5 mph.

Saturday A 30 percent chance of showers. Partly sunny, with a high near 72. West wind 6 to 8 mph.