Theories on why COVID19 is fatal to some and only mildly symptomatic to others
techtudor.blogspot.comHere are two papers that provide data suggesting temp and humidity are real factors.
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3551767
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3550308
Seems like a lot of people staring at correlations without a lot of causal reasoning (why is hotter, wetter climate worse for the virus? Is it because of more background bacteria? Is it just a way to find the omitted variable of exposure to sunlight etc etc).
That being said, pretty maps!
I understood that ultraviolet light is a good sterilizer. There's more light in summer. Maybe that covers it.