Average temperatures should be looked at seriously by researchers, to see if there's any correlation between the outbreak intensity & the region's temperatures.
I guess I could do it myself, with all the data at hand. Just looking at the data in a rudimentary fashion, it looks encouraging (for the northern Hemisphere....maybe not as positive for New Zealand and parts of Australia...)

Hong Kong's mean temps are MUCH higher than the hotspots of Korea, northern Italy, Qom (Iran), and others.
(Qom, for instance, hovered around 0ºC at night up until only few weeks ago...)

Spain might be the only anomaly in the top 12 affected countries where the climate isn't quite as cold as others, but Madrid, La Rioja and Álava/Araba (cities/regions with many/most of the cases in Spain) it also dropped to around 0ºC at night back in Jan and Feb.)

If I have some time over the weekend I could analyze this more in depth...