It is interesting to think about, but weather does play into church growth. In honor of the 109, 109, and 108 for Tues-Wed-Thurs in Dallas, Texas I'm using a couple minutes of my lunch break to just share some thoughts about this. It might be tempting to believe that in Canada and far Northern parts of the USA excluding the Northwest, evangelism in some forms outside of friendships is limited by cold weather. If there is ice covered by snow covered by ice then some more snow, and it remains below freezing, then you might not want to go 'door to door.' As obvious as this sounds, it might explain the trouble trying to reach people in colder climates in North America over 150-200 years. Not only might the French Quebequios be cold to evangelicals, but over time it could be a worse and worse reaction, since there aren't mediating influences. They can just hang onto traditions without much challenge. The internet changes some of this, as does global connectivity, but a personal challenge is harder to come by there.
In the South, with particular sights on Texas, this thought would not seem to hold. If from June to August many years (not all) you have temperatures in the 100's, people aren't going to use the plethora of outdoor outreach options as much. Yet there are still a large # of churches, many of which began before the advent of A/c in every house. Since then they've picked up people moving from around the US to Texas, and notably in Texas other places too causing rapid growth on top of that like Pakistan/India/Mexico, who at times trust Christ (or already know Him others) and join those long existing churches (if they are still viable, alive churches anyways). That kind of reactive receipt of people is a nice plus for those over time. Still what of intentional, proactive outreach? It has to be creative. Of course, the summer months are where people check out emotionally and mentally from church in the South. So perhaps 100+ is less of an issue for Texas, whereas in the nose to the grindstone months in Canada, the church is limited. This would explain some of their lack of engagement with other traditions, beliefs, and such; beyond reading about them or traveling elsewhere over centuries.
It would be interesting to see if anyone else has done research on this sociological aspect of the Great Commission.