You can actually put it on the balcony for about 20 minutes, then bring it inside to a perfectly level surface (determined with a carpenter's level). Your kitchen table will do, if it's level. Have everything ready to go ahead of time. And then calibrate before it gets warm. You don't need to chill your home.
We've had some heated (pun not intended) discussions here about putting the Phantom in the fridge for 20 minutes before the IMU calibration. That works just fine, too. A refrigerator is not below freezing, and it's not humid inside. I'm a former ski-racing timing official. We handled complicated electronics in much colder conditions. I use the fridge in the summer, and have never had a bad flight.
You only need to calibrate the IMU when your Phantom may have been bumped badly during travel, after a firmware update, or if it seems to be flying oddly.