We have hinged window awnings on our coop windows and love them. I would extend them past the length of the window to keep rain and snow from blowing in the sides. Ours aren't long enough so we now have sections of shower curtains attached over the corners

. You also don't have a lot of room above the vent, so a chain may not work, but you should be able to attach some kind of rod/pole to prop them up(I'm thinking of the way RV awnings are propped up

). Also make sure your roof extends over the top edge of the awning as there is a gap from the hinge. Whoever originally built our shed didn't add any overhang to the roof so we had to add flashing to keep the rain from leaking in the windows.
View attachment 2900539