Why was there only frost on my front and rear windshields this morning but none on the side ones?

Question

Parked on a shaded street, so I’m guessing it’s not the sun? Stumped though.

In: 26

Answer 1

Were the windshields facing the sky, while the side windows were facing buildings? Buildings shine in infrared, transferring some heat to the things they shine on, while a clear sky is black in infrared.