Cloud suck is a phenomenon commonly known in paragliding and hang gliding where pilots experience significant lift due to a thermal under the base of cumulus clouds, especially towering cumulus and cumulonimbus. The vertical extent of a cumulus cloud is a good indicator of the strength of lift beneath it, and the potential for cloud suck. Cloud suck commonly occurs in low pressure weather and in humid conditions. Cloud suck is especially dangerous for paraglider pilots.