I tried to use my STI (A4M9) over the weekend and it was completely useless. outside temp was -23F and inside temp in my car was 6F. The STI K band alerted for 15 minutes before i shut it off (automute is great). When i tried 20 mins later it kept alerting again continously for 10 minutes before i shut it off. in other words, it was pretty worthless. It worked fine today, but its much warmer now than it was over the weekend. i believe the operating temps is 20 degrees F or above until 120F. my GPS however worked fine as did my ipod and FM radio tx along with my car and its electronics.