As Elheapo said don't put it in the fridge, it will cause damp air inside the P3 to form moisture, that's not good for the motors or the electronics or camera
People cool their P3 for IMU calibrations as it gives a faster start up time
The best way I've seen it done is to put it in your car then put the air con on, a cars air con is dry air but cold air, so no moisture issues as such as the system removes that element
Once it's been in the car for maybe 10 mins or so, take it out and go indoors and place the P3 on a flat surface then do the IMU calibration
You need to do it as soon as possible as the P3 starts to warm up as soon as it's turned on so do it straight away
You can also do the gimbal calibration afterwards on the same surface
I'm just learning about all the calibrations to do before hand to try and get the basics right before I fly