I don’t know. Considering how many ridiculously cold-in-the-winter places making this list (Rochester, MN, I’m looking at you), I’m guessing that “pleasant weather” isn’t a huge component in these livability ratings.
When making our retirement requirement list, the top 3 were weather, international airport within an hour and decent hospital near by.
We made a 7000 mile road trip to find the perfect place. Ended up in the California Gold County. Arranged our finances to fly under the Calif taxes and we ignore the politics.