When Jonas discovers how much the community controls the climate, it helps us know more about the community. Specifically, it tells us just how committed the community is to enforcing "sameness."
Jonas finds out that there used to be this thing called snow. And that there used to be sunshine and rain and things like that. Somehow, the community has learned how to control these things.
This is really most significant because it shows us how important sameness is. It shows that the community does not even want the weather to vary so that there will be less variation of any sort in their lives.
In the book "The Giver" Jonas' discovery of climate control is another symbol of exactly how everything about life in the community is controlled. Jonas had experienced snow and the temperature change. He wanted to know why those things no longer exist. The Giver explained to him that the elders had decided to have climate control.
Jonas does not really fully understand the concept of sameness but he is beginning to. In chapter 11 he learns of sameness and why even the climate is the same. The Giver explains that snow made it difficult to grow food, by limiting agricultural periods. Weather shifts had also made it difficult for transportation.