I had one of those
round window cling thermometers, probably about 6" in diameter. It fit perfectly on the window on the side of the slide and was in a good spot to read from inside.
Had.
Brought the slide in and heard a terrible crunching noise. Fortunately the thermometer just crushed and didn't break the window.
Now I just look at my phone to see what the temperature is somewhere in my current zip code but it isn't quite the same.