I'm going to introduce you to the mysterious force of nature that I call Windowsuck. You may be aware of it already, or perhaps - as I was - only vaguely aware until now. I do not believe that Windowsuck is one of the primary forces of nature. I believe it is a simple corollary of something else, Murphy's Law perhaps.
You can easily test this force yourself if you live in a home with windows and window sills. I think sills are a priceless space for storage, but if you disagree with me, then please prepare for your experiment by closing a window and loading up a typical sill, perhaps with a coaster for a glass, some pill boxes, a pack of unpaid bills, a notepad and a stack of rubberbands. NOTE CAREFULLY that the sill is full of stuff that do not share physical space with the window itself! That is, by peering down you can verify that there is a little open space between the contents of the sill and the window. Now open the window and go elsewhere. Make sure no human or pet approaches the window for several hours.
when you return to the window, try to close it. You can't! Invariably, part of the stuff on the sill has drifted towards the window, and when you press the window down it will crunch on something. Windowsuck has worked its magic! (If you believe the prevailing wind direction is to blame, you can repeat the experiment on the other side of your home; you'll get the same results.)
I suggested above that I was only vaguely aware of this force, and I was always frustrated at having to rearraange a sill to close a window. But now that I know what's going on, I'll be more tolerant of this nuiscance. I think.