Sara Kim made this cute short as a student at the Vancouver Film School. You know how young men never dress for the weather, because it's not "cool"? This guy learned his lesson. Are you disappointed that it's not a love story? Think again, as commenter Annika Heydl explains it to us.
maybe I'm overanalyzing but I saw this as a metaphor for their relationship progression. He met her and was totally unprepared for the feelings that she would ignite in him, so he got figuratively "caught" in the weather that symbolizes his emotions. These get stronger, notice how the weather goes from some rain to a sudden tsunami, and he gets (figuratively and literally) swept away. She however, was inmune to all these feelings, and went through life as if nothing had happened because she was prepared and armed against the weather conditions beforehand. this continues until he decides that maybe he too should protect himself against these huge unexpected weather conditions (meaning he repressed his feelings), but just then, she comes completely unprepared (meaning she too develops feelings for him), and so they brave the weather together. Love this animation with all my heart.