Remember to open the warm air onto windows at the highest level, otherwise the rain will freez and block your front windshield, which is very dangerous. in such case, windshield wash does not improve but worse the vision. I made such a mistake once on Queensway and tried to clear the ice while stopped at an exit side, but did not work. later I realized the trouble and open the warm air. I am still scared whenever I recall the trouble.
Of course, you need to drive very slow and more carefully.