[David Lyga]

I hate to challenge SIWA but I have processed C-41 at both 80 F and 100 F and gotten the times to match the contrast (through much trial and error) and have obtained virtually identical negatives. The time factor I use for this is 1.05. In other words, if 3 minutes is perfect for 100 F you use about 8 minutes for 80 F. 1.05 X 3 on your calculator, then press = twenty times to drill down to 80 F. (However, with some calculators you must put in the '3' first, then the 'X' then the 1.05)

This is my experimentation and I offer no theoretical justification for anything with this (as would PE). However, it might be fun to copy my attempt and then see how you feel. As pentaxuser inferred, this can be quite a boon for saving frustration with the varying seasons' temperature changes! - David Lyga