I believe the reason some of us react differently to the heat is likely to to be related to how we cope with heat.
Some people feel more comfortable in the cold and some more comfortable in the warmth.
As we know stress and discomfort can raise our blood sugars. So, if you don't like the heat, I would expect insulin resistance to rise.
For me there is also a relationship between weather and how much I move. In the summer, I spend more time outside walking, running, cycling, gardening, walking to the shops, to the pub, etc Whereas, in the winter, I wrap up indoors away from the cold and wind and rain. I may be more tempted to drive to the shops to avoid getting cold(er), wet or blown away. And the exercise will make me more insulin sensitive.
So, I feel the way our insulin sensitivity reacts to change in weather is at least partially related to the way we react to the change in weather.