i think it is more of a time thing vs temp

my 95 mystique would grind second pretty bad in the winter, I used valvoline high milage with friction modifier, and if the car warms up some, turning the trans with the clutch out, I noticed last winter in the very cold that there was no grinding and shifting was very smooth

- 95 Mystique LS - Zetec/5spd - 99 Contour SeVT Sport - Duratec/5spd Official NE-CEG Contour/Mustang Family