I looked for answers, but didn't see any solid answers for this particular question. Unlike the other questions my winged humanoids can have their wings disappear so they can pass for human, then have them "grow"out of their body in seconds when they wish to fly.
In summer there's not as much problems for these humanoids to extend their wings. Males can wear the right loose tank top with lots of space near the armpits and extend their wings without problems and there's plenty of backless clothing female winged humanoids could carry with the right bra choice. Outside of summer it becomes difficult as I think there's little to no clothing that can pass for normal and still allow the winged humanoid to extend it's wing and fly when in a pinch (or when it assumes it's wings and flight won't be seen by people who would be alarmed).
Assuming the humanoids have access to tailors (who know about winged humanoids) that can change regular clothing to fit their needs, how would they change their clothing so as to have the full benefit of the clothing and wings?
About the wings: The wingspan is large, let's say a single extended wing has 1,5 times the length of an extended arm (if that's too little surface area make it larger). Growing the wings back happens at a speed the humanoid determines, but at a maximum speed of 3 seconds. It'll simply grow from a tiny thing attached to the shoulderblades and eventually be attached to the shoulderblades (ignoring the massive extended chestbone you would need to flap the wings) and the spine. The humanoid has full control of the wings during growth and can try to push them through something if possible.
My only idea so far was to have 2 seams run along the back around the shoulderblades. These seams cover up a zipper opening with flaps around both sides (inside and out) of the zipper to keep the wings out and make it comfortable to wear. If they want to extend their wings, they reach around their back into the seam, open the zipper and then take off. Zippers would probably not be a great idea since they would probably chafe and damage the wings no end when growing and flying, but using buttons or similar would likely not close off the back enough to keep out rain or cold wind.