It flashes and rumbles, and Nico and Emmi are a little scared. Is a thunderstorm dangerous? Where do lightning and thunder come from? How and why do clouds form, why does it rain, snow, or hail, and where does the wind come from? Questions that the children's uncle can answer, as he is a meteorologist and is secretly called "Weather Frog" by Nico and Emmi. Together, they visit a weather station and look at the measuring instruments. They observe clouds, the formation of a thunderstorm, sail on Lake Garda - and Nico almost got lost in the fog on Grandpa's birthday. A narrative non-fiction book for elementary school children with numerous illustrations and photographs. The text for the back cover was written by the well-known diploma meteorologist and TV presenter Sven Plöger.