I think it depends on what you plan to do with it. Other than Phoenix, I'm in a VERY hot area. 110F in July and August many days, with 114F not unusual. But I'm not worried about it because I don't fast charge, and if needed, can even trickle charge on hot nights. There is a 10 year degradation warranty. And I am only putting about 600 miles per month on it, about 20 per day. But most of all, I plan to sell it / trade it in within a couple years so degradation shouldn't really be an issue.
So I think the heat is a question also on how you plan to use it and how long you plan to keep it.
Don't get me wrong, I want it to last, and I'm trying to take good care of it. I charge it only between about 3-5am when its cool, etc, and I plan to report the numbers here. But for the cost to me - about 15.5k - it was an easy decision over a used 2015 for 10k. It hands down beats my truck for the 13mpg I was getting driving short trips around town every day.
2018 Leaf SV Pearl White with Tech and All Weather, Purchased New on 5/3/19