Towering cumulus cloud indicates rising air. Usually little if any rain during this stage. Lasts about 10 minutes. Occasionally lightning during this stage.
Most likely time for heavy rain, frequent lightning, strong winds, and tropical cyclones. Storm occasionally has a black or dark green appearance. Lasts an average of 10 to 20 minutes but may last much longer in some storms.
Rainfall decreases in intensity. Some thunderstorms produce a burst of strong winds during this stage. Lightning remains a danger during this stage.