Timelapse footage of classic cumulus clouds. These clouds form due to solar heating of the ground, which warms the air above it, causing it to rise to a level at which it's cool enough for the moisture to condense. These clouds are at an altitude of around 1500 metres (5000 feet). These are cumulus mediocris clouds, which have modest vertical development, but they are generally a fair weather cloud. In an unstable atmosphere, cumulus clouds can develop during the day into towering clouds that may form thunderstorms. Filmed in the USA on a spring afternoon.