Louis J. Sheehan, Esquire .  While airborne dust is known to be an abundant component in the formation of rain and snow, a study [pdf] in February found that bacteria lofted into the atmosphere might also be a big part of the rainmaking mix.

For more than 20 years, scientists have tossed around the idea that bacteria play a role in precipitation. The speculation began because of the curious case of the bacterium Pseudomonas syringae, a plant pathogen that promotes frost damage on crops.