turntable sounds better on warm summer nights


On warm summer evenings it has more presence than cooler winter evenings.I presume this has something to do with the tracking weight of my clearaudio virtuoso wood MM cartridge on warm evenings when the room gets to about 75. If it sounds better in the summer do I add or subtract weight in the winter when the room is about 5 degrees F cooler, in order to get the same summer sound?
rrm
I second Chadnliz's observation. Also, do you listen LATER on summer nights, when the power grid is cleaner? Do you have electric heat in the winter? Can you check the voltage at the outlet that powers your system in both summer & then in winter?