A research team from LSU, Montana and France had found evidence that rain and snow are started by bacteria who are able to catalyse precipitation at lower temperatures than grit and dust:
Dust and soot particles can serve as ice nuclei, but biological ice nuclei are capable of catalyzing freezing at much warmer temperatures. If present in clouds, biological ice nuclei may affect the processes that trigger precipitation…
But, what makes this research more complicated is that most known ice-nucleating bacteria are plant pathogens. These pathogens, which are basically germs, can cause freezing injury in plants, resulting in devastating economic effects on agricultural crop yields.
