Cumulus humilis, with cumulus congestus on the horizon

Cumulus humilis (from L humilis, humble) is what is commonly referred to as "fair weather cumulus". These clouds typically occur at 500 to 1000 metres altitude and rarely reach 2000 metres. They indicate modest warming in the lower atmosphere, as can be expected in fair weather, but show no significant vertical development, indicating that the temperature in the atmosphere above them either drops off very slowly or not at all with altitude. While cumulus humilis may be accompanied by other cloud types, when they appear in a clear sky (see picture), they are an indicator of pleasant weather for the next several hours.