The antifreeze shrinks in volume as it gets colder and expands when hot.
The maximum level will occur when both motor and radiator are hot. In cold weather the water in the radiator doesn't stay as warm when you're driving because of the colder air moving through the fins cooling it easier. So the volume of that part of the water in the system is less even when stopped after driving some miles.
In the colder temps the motor gets colder overnight than when outside is 50-60. So the water inside the motor shrinks in volume also. This means at 30 degrees the total volume will be substantially less than when the temps outside are 60 and the motor was driven a few hours ago; the water inside the motor is still warm after hours of sitting.
Change from week to week checks at totally cold temps are the best comparison I find. The volume hot in cold weather depends a lot on how the car has been driven and on the outside ambient air temps moving through the radiator. I mark the level on the recovery tank with a Sharpie at the temp I want to compare with later.
Dual auto air on both