Giant and ultragiant aerosol particles can play an important role in warm rain initiation. Recent aerosol measurements have established that particles as large as 100 μm are a regular part of the atmospheric aerosol. When ingested in growing clouds, these particles will produce a tail of large drops on the upper end of the cloud-droplet distribution. In a series of numerical computations, this tail of large drops was found to be a significant destabilizing factor which can speed precipitation development. Abstract Giant and ultragiant aerosol particles can play an important role in warm rain initiation. Recent aerosol measurements have established that particles as large as 100 μm are a regular part of the atmospheric aerosol. When ingested in growing clouds, these particles will produce a tail of large drops on the upper end of the cloud-droplet distribution. In a series of numerical computations, this tail of large drops was found to be a significant destabilizing factor which can speed precipitation development.