I love the south. I would HATE to live in the south. Any place hotter than Chicago in the summer is completely impossibly miserable to me.
I think the worst weather in the US would have to be Las Vegas area, or any other desert area where it gets over 100 deg regularly.
If we are talking about seasonal, then I'd say draw a radius of about 500 miles around New Orleans. That is the great circle of 24 hour daily summer sauna.
In the winter, I think probably places like Barrow or other very low density places with lacking connecting infrastructure would be the worst due to logistics problems. Even if the weather is tolerable due to not too much wind/heavy snow, and one could go dog-sledding, skiing, snowmobiling, or out playing in the woods ... The fact that my Amazon packages would be late would be upsetting ...
my favorite weather --- Door County area of Wisconsin ... in the summer, it is generally about 10-15 degrees cooler than Chicago. If it's 90 in Chicago, it's around 80 in Sturgeon Bay. If it's 100 in Chicago, it maybe is 85 or so in Sturgeon bay. Can be pretty hot/bad during the day, but, almost every evening it's beautiful, AC rarely needs to be run at night.
I'm sure much of Michigan would also have similar agreeable weather.