I have the same tires - the spec's say that anything below 7C and the tires are as hard as hockey pucks. At this temp point or below, the rubber won't warm up and unless you can put up with the thumping until they warm up at highway speeds I would change to winter tires. There is also the lack of grip because the tire compound has not been designed to operate at such low temps's - not enough silica in the rubber to remain flexible.
I store my car on rubber mat's - about 2 inches think under each wheel with 50psi in the tires when I park it in Nov. By the 1st or march when I pull it out it will have about 40psi all around I suspect.
We haven't had a lot of snow this year but without PSM or TC options and along with fools in lowered Honda's flying around without snows on - I don't need the hassle of someone hitting me. Besides, my car has never seen snow and hence - SALT, so I'm not starting now.
