Ralphie is upset because it’s so horribly hot and he wishes that it would go ahead and rain. Ms. Frizzle takes his comments to heart and she decides to take the class on a fieldtrip in order to soar through the skies and to forge the proper conditions that would cause it to start raining. However, they soon discover that nature is a complicating thing and that the conditions need to be perfect in order to get the outcome that they desire.