Freezing rain usually occurs when you have an inversion aloft, resulting in above freezing temperatures over sub freezing temps, along with precipitation. The snow that falls melts, then chills down as it goes through the cold near surface layer. So when it hits an object, it freezes on contact.

For this to occur, you need temps to be pretty close to freezing, as if it's too warm, or won't refreeze, and too cold, it never melts to rain.