Many people own and operate EV's in colder climates.
@AAKEE, in particular, does an excellent job in this forum of showcasing how EV's can be successfully and happily used in very cold weather.
That said, the OP raises an excellent question. My short answer to that is yes, extreme cold weather absolutely poses a threat to the long-term health of EV battery packs. Those threats can be be mitigated by taking steps such as those outlined by
@AAKEE . But ignoring weather and just driving the car and assuming that Tesla will prevent anything bad happening is, unfortunately, just not true.
I love Tesla and what they've done. But it's helpful to understand that what is good for Tesla is frequently not good for individual Tesla owners. DC Fast Charging is an example of that. Tesla engineers things so that you get in and out of their Superchargers as quickly as possible. Both so it's a favorable user experience and so your quickly leaving frees up the stall for the next driver. And the community word-of-mouth does a great job of touting how great that all is. YouTube has countless videos celebrating the very high charge rates achieved when someone rolls into a Supercharger at a low SOC. And disappointment if they don't hit whatever charge rate milestone they were hoping for.
The almost-never-spoken secret is that, for those EV owners who would prefer to prioritize battery life over YouTube likes, a lesser charging rate and less heat put into the battery would be far better for long-term battery health.
Degradation of Lithium batteries is a fact of life in the EV world and it cannot be avoided. Buy an EV and you're going to start losing capacity the moment you drive it off the lot. It's discussed incessantly in forums like this, for good reason. And because we have all those discussions, common wisdom like not maintaining high SOC's any longer than necessary, or minimizing DC Fast Charging... become well known.
What doesn't get discussed very much is probably the worst thing that can happen to your EV battery pack: Lithium plating.
Lithium plating, like calendar aging or cycle aging, is going to happen. But like those other degradation mechanisms, there are things you can do to slow it down; and there are things you can do that speed it up.
Lithium plating begins accelerating significantly as temperatures fall, and as C-rates (how fast you're charging or discharging your battery) rise. Do both of those at the same time and you've entered the worst of all possible worlds.
But won't Tesla's BMS protect my car?
Tesla's engineers are, of course, well aware of all these issues. They
try and protect your car. When we see the blue snowflake or the bacon strips we know the BMS is limiting functions like regen and charging speeds for that very reason.
But Tesla is limited by physics. If your pack is cold-soaked after sitting outside overnight in very cold temps, it's going to take quite awhile before the BMS can get the pack even moderately warm. And Lithium plating can occur at surprisingly moderate temps.
Tesla engineers are also hamstrung by the need to not use too much energy to do things like protect the pack. There are already countless people complaining about "phantom drain." So the engineers do the best they can, considering that - broadly speaking - they're dealing with an uneducated population of users.
Like most of the effects involved in Lithium battery degradation, Lithium plating is not a thing that happens at a discrete, definable threshold. It has been observed at C-rates above 2.0 even at 50C (122F) (which is why Tesla preheats the battery to such high temps when navigating to a Supercharger). It has been observed at 25C (77F) at C-rates of 1.0. And at 12C (53F), which most of us think of as quite moderate, it has been observed at a C-rate of 0.5.
The deal is this: as temperatures decline, the C-rate at which Lithium plating begins to happen declines as well. In extreme cold conditions, the C-rate at which significant Lithium plating risk exists is quite low... almost certainly below that which our cars' BMS limits us to.
Yes, the BMS helps limit the damage. But Tesla would sell no cars if they engineered things so avoiding Lithium plating was the biggest priority.
The big picture for Tesla is getting nearly all of us through the warranty period with no more than 30% battery degradation. That's not a very high bar.
For those of us who wish for better than that, getting our pack warmed up before we use it to drive, or before we charge it, is probably the nicest thing we can do for it.