the low-temp does definately have an effect though, I live in Calgary AB, Canada so I expirience +35 to -39 (yesterday) and I can say for sure that in the cold the pads grip less. I'ts to do with the thermodynamics of rubber and how heat effects the viscosity (softness in terms of rubber) of it, the more viscous it is the higher the friction = grips better on the rim
My Spanish Fly pads worked great when I first got them, but because of the smooth factory finish it only took one drop of water to give 0% braking power. Now they are better but still almost unusable in wet conditions for trials.