As I think docj mentioned, the "study" was done by Marko Kolanovic, a JP Morgan quantitative and derivatives strategist. I've been unable to find the actual report, but even if I did, I have two problems with it from the getgo:
Marko Kolanovic appears to have no credentials in infectious diseases.
Marko Kolanovic appears to have a conflict of interest. Showing no need for further lockdowns would improve JP Morgan's business.
Expertise and conflict of interest avoidance are necessary factors in any good research.
There are other, more important, factors besides weather, but you're making the classic mistake of confusing correlation with cause and effect.
For example, shoe size is correlated with intelligence. In general babies are dumber than adults and in general babies have smaller shoes than adults. However, saying that larger shoes is a cause of increased intelligence is probably not true.
No, no, no. That's not how it works. When you make a claim, you have to support it with proof.