Why is the transmission of the memory of snow exhausting to the old man? What does this reveal about the community?

After the Giver transmits the first memory of a sled ride down a snowy hill to Jonas, he is exhausted and physically drained from the experience. The reason that the Giver is extremely fatigued has to do with the fact that the memory took place in the distant past. In order for the Giver to retrieve the memory, he had to bring it back from many generations ago, which is apparently a difficult and exhausting task. The Giver explains to Jonas that the further a memory is in the past, the more difficult it is to retrieve and transmit.
The memory of the snow is significant and reflects the dramatic changes Sameness has had on the landscape, climate, and environment of the community. Sameness has eliminated hills and treacherous weather in order to make life more efficient and comfortable. Harsh weather like snow and rough terrain no longer exist in Jonas's community. While there are positive aspects of Sameness, it becomes apparent that there are also negatives attached to the altered environment and lifestyle created by Sameness, which become more pronounced and controversial as Jonas's training sessions continue.

In The Giver, the first memory Jonas receives is one of snow. Jonas experiences the feeling of cold air, snow, a hill, and a sled. Once the Giver ends the transmission of the memory, he is exhausted. This is because the memory he gives is an old one from generations earlier. The Giver explains that the memory was old when he first received it too. It must be brought forward in his mind before it can be transmitted, which takes a toll on the Giver.
Jonas questions why he has never seen snow before. The Giver explains that the community does away with anything that negatively impacts Sameness. Snow affects agriculture production. Climate Control ensures that agriculture production remains predictable. Since hills affect transportation, doing away with hills ensures predictable transportation.