Even if there isn't snow on the ground, winter tires can and do help keep a car under control. The performance tires that come on the Porshce, BMW or even the Honda S2K are going to give you no traction at 45 degrees and lower. That same corner you can make all day long in the summer has the car severely understeering when it's cold. Someone pulls out in front of you on that cold morning and instead of stopping on a dime you are hoping the car stops before hitting them.
So what do you do? You get a set of four winter / snow tires. They are going to work better in dry, cold weather as well. The Bridgestone Blizzak LM-60, Dunlop SP Winter Sport 3D and the Michelin Pilot Alpin PA3 are all very good options -- in fact, much better options than parking the car all winter long.
Don't let Old Man Winter get the upper hand.