One somewhat awkward feature of 981 Boxsters is the gap(s) between the folded top and the body. The top on mine, has been down pretty much since the spring, and although the car is garaged, it spends enough time outside to have fall leaves make their way into the gaps, mostly near the fenders, but also along the middle. As it was chilly enough this morning to put the top up, I first noticed bits of debris on the big inside horizontal panel. (Easy enough to see by looking down through the rear window.) Looking farther along the sides, down into where the top cables are, I saw more leaves. It was tricky working a vacuum cleaner hose in there, but worth the effort. The picture below is blurry, but will give you an idea of where to look.
Driver's side, seen through the rear window:
Minus 40 degrees... Is that Fahrenheit or Celsius?