Cumulus Latin:(Mass) probably the most common of clouds and on sunny days when the land is heated by the sun these clouds form. With all their bases at the same level they create cloud streets, the up currents of warm thermal air currents forming cauliflower shaped clouds as water vapour condenses. the small clouds may only last 10-15 minutes as they evaporate as they drift away from the thermals that feed them. They form in mid morning and are more extensive by mid afternoon. They're height is determined by the height at which the rising air cools to the same temperature as the surrounding air.