They could fight and win this, there is an assumption that it would be fit for the purpose it was sold. It is for sale in the market so regular occurrences in that market would not absolve Tesla or responsibility. It is fair to assume a car for sale in an area can drive in an area.
There is also a sale of good provision that relates to pricing, basically if you buy really cheap headphones you can't complain when they break but if you buy a very expensive pair there is an expectation of quality and that, relative to their price, they will last for some time.
Where did anyone mention a tornado? The specific reference to the weather was "not abnormal for this locality" and the Tesla rep said it was because it had been driven in the rain.
Your view of if its cheap or not doesn't get them out of being a premium brand, there is an expectation of quality associated with the price point and branding. Namely that rain won't render it useless until you spend 20k.