Good tip *NM*

The lower ones are fairly deep and have what I imagine are (appropriately enough) boxer fans. When a leaf gets stuck in there it can sound like the classic baseball-card-in-the-bicycle-spokes. Perhaps if it breaks up and goes into the engine compartment it'll eventually find their way to the ground, but if not, its not good to have that junk accumulating wherever in there. I find that using a fairly small, flexible twig to gingerly poke around can usually dislodge leaves and allow them to be gently dragged out. (Better done without the fans running, of course.)
The engine induction air sections have slats to prevent big stuff from going to the air cleaner(s) but it's still a good idea to regularly do a visual check. As they're shallow, it's easy to pull stuff out.

Minus 40 degrees... Is that Fahrenheit or Celsius?

I just pulled a couple of long pine needles out of my right side intake.