Cumulus - Forecast

Forecast

Cumulus humilis clouds usually indicate fair weather. Cumulus mediocris clouds are similar, except that they have some vertical development, which implies that they can grow into cumulus congestus or even cumulonimbus clouds, which can produce heavy rain, lightning, severe winds, hail, and even tornadoes. Cumulus congestus clouds, which appear as towers, will often grow into cumulonimbus storm clouds. They can produce precipitation. Glider pilots often pay close attention to cumulus clouds, as they can be indicators of rising air drafts or thermals underneath.

Cumulus clouds can also produce acid rain. The acidity is largely formed by the oxidation of sulfur dioxide, the most plentiful acidifying gas, into sulfate ions. The main oxidizing compounds are hydrogen peroxide and ozone. Various nitrogen oxides can also react with hydroxide ions to form acids.