What do girls mean by using the same sky but different weather?

Girls say "the same sky but different weather" means that two people are under the same sky, but their moods or emotions are different. This sentence implies that these two people have different feelings or States in some ways, or that their lives or emotions are at different stages. In addition, this sentence can also express girls' concern and understanding for another person. She knows that even if the sky is the same, everyone's experience and feelings are unique.