I have a Model S 60. Today I was driving back home, starting with a around 205km (rated) range. My journey was only 140km and I figured I had plenty of range. After 120km of fast driving in rainy 5 degree (celcius) weather, we arrived in our city (20km from home) with around 70km of range left. So we used around 135km of our rated range. We stopped to meet some friends and grab a bite to eat, leaving the car parked outside for around 3-4 hours. When we got back to the car to head home, we only had 50km of range left. 20km seems to have magically disappeared. Luckily we only needed 20km of range, but even though I drove home slowly i relatively flat conditions, by the time we arrived back home we had consumed another 30km of range. Okay there are many things that can affect actual range, but what the hell happened to that 20km of range in the 3 hours while parked? It's not like there was an extra 4kwh consumed, and yet it was no longer there. Is it the cold weather perhaps? Would the warm battery show greater range and as the battery cooled over that 3-4 hours, there was less accessible energy, and therefore reducing available range? Does this mean that Tesla's range estimates do actually take battery temperature into consideration? It was very disconcerting. I'm only a new owner, so I haven't become accustom to these quirks yet. Is this normal? If yes, I need to plan better to ensure I have a sufficient buffer to reach the next charging point.