[wparsons]

Ambient temperatures don't matter at all for a tire. What matters is track temperature, and how much heat you'll be able to get into the tires.

At 50F (10C), any typical good summer tires will still get plenty of heat on a track. At 25F (-3C) you're might be below what a ZII/RS3/Rival/RE11A/etc will need for heat, BUT if it's sunny out the track temp will probably be high enough to get them working well too.

Are you just lapping in the cold? Have you tried typical summer tires yet and found they don't build enough heat? You can always drop the pressure a few psi to help build some heat as well.

I know at an autox last weekend it was under 10C but when it dried out there was lots of grip on typical summer track/autox tires.