In general, the warmer the rubber (thermally) the softer the tire. The softer the tire, the more able to conform to road irregularities and this conformal characteristic at the tire/road interface is a significant contributor to traction.
But when you are as wimpy as I, you rarely approach any kind of limit. I know that on warm dry roads the scooter will hit the hard parts before I'm near the traction limit. I'd guess that the same is pretty close to true at any kind of temperature you would ride in. As conditions become marginal with loose debris (e.g. sand, rubble etc.), this warm/cold difference may be more apparent.
Ridin' the IceBurg - 10% transportation, 90% fun!
90K and counting.