Heat lighting refers to thunderstorms past the horizon, generally thunderstorms far enough away that you do not see them.
Grassfires can be started while it’s raining, a lightning strike does a good job of drying out the grass around it, and then the ensuing fire will dry out the next bit of grass.
Generally, if there’s a storm generating lightning, it is at least raining a little. That rain can evaporate before it hits the ground.
Les is right, however, on the actual question (since other than rain, you get snow, volcanoes, etc.)