No beeping from my car even in temps lower than 45 degrees. I can't see what difference a lower temp of 45 would make anyway since that's still well above freezing.

Do any of your dash icons light up when the beeping starts? Have you gone through the owner's manual to find all conditions that will trigger an audible alarm? Have you installed any electronics such as a nav unit that may be set to beep at 85 mph? At any rate you have an amusing speeding excuse to provide to the police should you ever get pulled over.