Many old British designed aircraft were equipped with storm windows. The Lancaster/ Lincoln series had them as well as the American DC4 and DC3. In blinding heavy rain when the wipers were useless (or u/s) the storm window (which was either part of the main windshield or just an aperture)could be opened by means of a gnurled knob or screw, and the window either opened inward, or slid along a rail.
Due perhaps to the vagaries of airflow past the main windscreen, there was very little air blast - just lots of noise.
But the view improved dramatically.
I had occasions when opening the storm window to get a clear shot at the runway in heavy tropical rain, was the only way to land. I could never understand why light twins such as the Baron, Navajo, Seneca etc never had a storm window as part of the windshield, particularly as for some strange illogical reason they were not fitted with wipers. And please don't tell me that the curvature of the windshield was such that the rain just fell off. Not in my experience, anyway.