What is the topic sentence of a good snowflake?

The last sentence of Good Snowflake: The same is true of good snow and clear snow in our life. At a certain time and place, it falls beautifully, and the falling snow disappears, but it irrigates our hearts.

Good Snowflake is a fresh and natural essay. In the article, the author depicts a wandering old man with a dirty appearance and a sad situation but a kind heart, so as to reveal the central idea of the article: no matter what the situation is, we should learn to give warmth to others.