A quick look is all you need to know if it's sweater weather or not. This accurate window thermometer suctions to the outside of the glass so you can easily see the degrees. The round gauge is more reader-friendly than a linear thermometer and has a bright red indicator for error-free reading. Place this outdoor window thermometer in a spot where you can easily monitor the temperature from the comfort of home. Polystyrene; about 4 1/4" dia. Gives readings from -40 to 140F.