The amount of ingress and Egress isn't going to change that drastically at peak times though? arnies don't fall off of taps at 5.30 then screw themselves back later on! as for the environment, at the moment the weather doesn't change dramatically enough for it to affect the levels at peak times.
With my basic knowledge of physic
cold weather will lower the resistance in the copper core of the cabling (lower temp = less atomic vibration = easier movment of electrons) so in theory *cough cough* levels should be better now that in summer.
but also at this time of year there is a loooot of moisture which is never a good thing.
and the upstream - modems do change upstream if the cant get a lock - you just said they do lol.