In this video, Bjorn Nyland attempts to show how road conditions affect range more so than outside temperature.
Nyland says that rain, snow, slush, etc. increase energy consumption in the Tesla Model S rather significantly, but temperature variations have less of an impact on how far the Model S can go.
"I explain how Tesla Model S uses the excessive heat to warm up the battery and inside the car. Because of this, outside temperature barely reduces the range. It's mainly reduced by rain and snow/slush."