I definitely do not recommend using summer tires in cold conditions, regardless of snow cover. Below 40F or so most summer tires really turn into concrete and have little to no grip. They're too stiff to grip the road. By comparison, I can still push my fingernail into my winter tires in 20F weather and they still have some give. It's as much about temperature as it is the tread pattern.
So far I haven't had any problems stacking a few sets of Star Specs or RS2s in the garage for storage. No problems in the spring back into autocross season, no cracking issues.
My STI was fine with good all season tires (I had RE960AS on it). Winters still do better, but it was more than acceptable.
We have a lot of weather fluctuation in Indiana and I have run my winters in 60-65F weather and my summers in 30-35F weather. Starspecs, RS2s, RE050 RFTs, RE070... All of them have trouble with traction, trigger ABS, and generally I don't feel it is safe before 40F or so.
Jim, perhaps it rarely gets down to those temperatures for you, so you may be ok, but here in Indiana driving on summer tires is insane in the winter.
I also agree winter tires compromise performance in warmer conditions. Really, it has to be cold enough to get the benefit, so it isn't needed for people in southern states. They're not great for 75mph cruising with a cross wind in 50F weather.
2009 BMW 135i, 6 MT, M Sport, DIY DCI, Cobb AP, Apex 18x8.5+9.5, 235/265 Starspecs
Last edited by Freon; 01-18-2013 at 04:41 PM.