Back in my racing day with motorcycles (sportbikes) we would have to warm suspension components up before we took our first hot laps. I think no matter what components you get they are all effected my temp. Some just more than others...
2005 Rocky Mountain ETSX, Surly Crosscheck, 2000 Enduro Expert (sold), 1999 Rockhopper, 1984 Trek 520 (STOLEN-but recovered!), $7 rigid MTB from a police auction (broken, then stolen)
The RST fork is probably an elastomer fork...so the flexibility of the elastomer would be very much affected by temperature. Air or coil spring forks don't experience such significant performance variations with temperature.