It depends how hot it is, our upstairs can get up to 40 degrees or more on the really hot days so when its like that it won't be cold but cool, otherwise it can be cold if you sit the temp down that low or if you have it on for a long time.
The kids rooms are smallish too so that helps also. We've been really happy with it cause it helps keep the room decent enough to have good night sleep, we do need to leave it on most night too cause once its off it heats up pretty fast. And we need to put it on at least 2hrs before bed to get the room cooler.
Also if your windows are wind out like ours its a bit harder cause you can't put the tube out without allowing hot air to re enter. If they're up/ down windows prolly will work even better.