One problem with this theory is Iran. While your graph depicts the Iran cases in the yellow area, much of Iran lies outside of it. Many of the diagnosed cases are in that yellow area, but there are many outside of there, and it is suspected that thousands more lie in the outer regions of the country and are currently undiagnosed.
In addition, Germany and New York are in an entirely different climate zone and are facing outbreaks, so that’s a bad sign as well.
Do we have an infection map of Iran? I’ve only been able to find national numbers, and they’re consistent with the disease primarily spreading in Tehran. [That said, I also buy that the numbers in Iran might be a 100-1000x underestimate at this point, which might mean this is just telling us about testing instead of infections.]
Here’s a province-level infection map of Iran as of the 12th:
here’s a climate map of Iran. Kind of hard to draw conclusion tbh.
Both some German cities and New York are listed as potential cities to be under increased risk soon (see the last image at the post) - they actually have pretty similar temperature/humidity profile.