I started using a cycling rain cape a few years ago. I made 2 out of ponchos. At some point I will buy one, but I am not commuting at the moment.
Cycling rain capes drape over your hands on the bars. They have internal straps you put your hands through to keep the cape draped over your hands and handlebars. They should also have an internal belt to keep the rear of the cape from flapping up.
The advantage of a rain cape is better ventilation, as the bottom is open and they keep your hands dry-ish. The disadvantage is that in heavy rain and wind you may get wet from side spray. Also, they can catch side winds, and make riding into the wind tougher.
But combined with a long front fender with a flap that just skims the pavement, I found riding with a rain cape to be very pleasant.
https://www.bikeforums.net/commuting...ape-1-2-a.html
https://www.bikeforums.net/commuting...0-success.html