If it's dry, the stopping distance is actually better on summer tires than winters, even at low temps. How low the temps can go before that potentially changes? I have no idea. However, looking at some tests that have been done on this:I'll leave you with a scenario here to ponder. You're traveling down the highway at 65 or 70mph and need to emergency brake. It's 5F degrees out. You end up rear-ending the car in front of you. Was it due to compromised stopping distance of your summer tires, or was it simply an unavoidable situation even in the best of summer conditions? Your opinion on it probably doesn't matter. Your insurance adjuster comes out to inspect your totaled R8 and notes... ah, you were driving on ultra high performance summer tires in the dead of a Chicago winter. Coverage denied. Why? Well, you were negligent, knowingly operating the vehicle with tires that the manufacturer states are only for summer use. This was a "preventable accident."
Do You Need Winter Tires If It Doesn't Snow? - YouTube
The TRUTH About Winter, All Season and Summer Tires ❄ Tested at 0c, 2c, 6c, 10c, 15c - YouTube
I personally still would choose the winters, especially since wet/snow would ruin your day, but the dry performance definitely caught me off guard.