My take on it is that people who are out of shape do not want to do anything in hot weather, not on an E-bike, on their feet or sitting in a chair. If you are in shape you will take the heat better and it will be why on very hot or humid days you will see mostly people who have some sort of physical training outside and those who don't are in air-conditioning.
On my last ride near a lake I saw a couple of couch-potatoes on beach-cruiser type bikes starting off on a route I like to ride, and I did not think much of them as it is a common sight. But after a dozen fast miles on my road bike I stopped where there was a fountain for a drink, as I had forgotten my water bottle that day. After the drink I waked my bike back over to the road and the couch-potatoes went whizzing by at what looked like a high-rate of speed, no helmets, no sweat and big smiles on their faces. I did not think they were on e-bikes yet, I just thought they had taken a short ride and turned around and were still very fresh, but when I got on my bike and followed them it was not that easy to gain on them, and when a very steep long grade came up where I thought I would catch and pass them like they were standing still, they shot up the hill without slowing at all and disappeared over the crest. After I got to the top of the hill I saw them far in the distance turning down a road, they were a quarter or three-eighths mile ahead, and I put my head down and ran up to over 20mph and slowly reeled them in just to get a look at their bikes, and yes, they were high-end E-bikes that had the batteries etc. very well concealed, one a "fat tire" bike the other with fat beach-cruiser type tyres. This couple had been sitting bolt-upright the entire time they were riding, and they had been riding at a speed over a distance they never would be able to on a regular pedal-powered bike, and that goes for any e-biker I am sure no matter what the temperature is outside.
