Tesla did test the Model S in the test center in Sweden where every car company goes to test winter performance.
I don't know if Tesla used a Swedish test center, if they did they probably used the test center Ford built when they owned Volvo. However, not every carmaker uses that one, there are a few winter test centers both in Finland, Sweden and Norway, that alot of car manufacturers uses, some use several of these.
There are also some things that come up because of new technology. Headlights for most of the history of cars were incandescent lights, and they became halogens over the last 20 years and LED headlights only became common in the last 10 years. Incandescent and halogen lights produce a lot more heat than LEDs, so they have a tendency to soften ice and snow if not sluff them off entirely.
This is where Tesla could just look at the other light manufacturers, like hella, Bosch, etc, they have long since put heat elements in their led lamps.
Halogen and xenon melts the snow in snowing and black ice conditions and keep their clarity, but in salty conditions they make the salt slush dry out and create a darkish coating on the lamps that can stick well when trying to clean them.
The last part is shadowing the lamps output almost as much as the ice build up on non heated led.
However, on xenons on 35w or higher the law states that you have to have a lamp washer, which makes much better driving experience then both the leds and the xenons from Tesla, this is also because Tesla made their xenons with less than 35w.
At low altitudes in the winter ice can build up on the nose and foul the radar systems.
This is also happening on our teslas, high humidity and minus centigrades.
@nimrooz careto elaborate on 110C difference?
That is 230f swing.
@SSedan on the summers, highest recorded air temp is usually between 30 to 40 c. Winters is usually around -25c. However, it's not all that unusual for the winter temperature here where I live to dip down to -35c/-40c and stay there for a couple weeks or days.
So my temperature difference mentioned earlier is on the car/sensor surface, or any other surface like house, garage door, etc.
So in air temperature, the difference could really easily be around 80c, surface/sensor/interior temperature differences between the winter and summer can easily be 110c. It's perfectly normal for a surface in the sun or glassed in interior in the sun to reach 60c/70c or more in the summer.
^^This^^
some folks are only happy when they have something to complain about.
-have you ever driven with ice and snow building up on your cars headlights in snowing weather, on curvy slippery roads through a dark forest at pitch black night?
I have to ask, because I have driven thousands of miles both in California, Florida, etc, Germany, turkey, etc. But most of my life I have been driving in Scandinavia and Denmark. There IS a huge difference in the driving of those places, in so much ways.
Whatever you are used to with your driving is usually completely different from another place with a different climate.
I remember my first time driving in a milder climate, I asked for a window and lamp washer liquid at the gas station, they didn't have a clue. They offered a spray bottle. And I was in shock that they never had heard of or used it. But every rental in milder climates only have water in their tanks, and it still smells wrong when I use the washer on rentals on vacations. I'm tuned to my way of life where you need a special liquid that doesn't freeze and cleans your windshield and lamps, others on other places don't need it and maybe have never experienced it or the smell of it.
-But is my needs only things I made up for myself to have something to complain about? Or do my needs differ from yours, due to anything from geographic location to local climate?