Capes/ponchos are great for rain, but act like a sail if there's any wind.
Not to be lumped together , Cycle rain capes are cones, that you put your head
thru the top.
a rain poncho is a big flat rectangle with a hood sewn in the middle.
Proper cycle rain capes are featuring a loop [ 1 for each hand], and a waist tie ,
they keep the cape under control is pretty stormy weather .
that is my experience, not hearsay.