Some of the coldest air so far this season invades southeast Wisconsin tonight, with overnight lows dropping to 18 degrees at the lakefront and 12 degrees inland under mostly clear skies by midnight. Tuesday will begin with sunshine and then more clouds roll in later in the day. High temperatures will stay in the mid-thirties even with the sunshine. Winds will turn more southwesterly and temperatures will take a turn upward for the remainder of the week. We will see high temperatures in the forties by Thursday and fifties by the weekend.