A thunderstorm starts to form when water evaporates to form clouds. Which of the following best explains why thunderstorms usually form on warm days?

Thunderstorms might form on warm days simply because heat is what causes evaporation, causing rain. Thunderstorms also form when the atmosphere is unstable! Meaning the hot air is above the cold air, evaporation occurs, it rains, and then rapid expansion of heat in the air caused by lighting causes thunder.