Shower of Black Rain at Castlecomer : 30th April 1887
The following article first appeared in the "Meteorological Magazine"
A very strange atmospherical phenomenon was witnessed at Castlecomer, Ireland, on April 30th. A general depression was felt all over the district in the afternoon, accompanied by lightning and thunder and a tremendous rainfall, which continued till about seven o'clock. At about 7.50 p.m., a thick black rain fell, sufficiently black to stain any white cloth, and apparently impregnated with an insoluble dust. The water of the local streams and cisterns was discoloured, and in many places could not be used for domestic purposes.
Castlecomer was a well known mining area. Mining began there as far back as 1640. The likely explanation for the black rain shower is that during the thunderstorm earlier in the day, some fine coal dust from nearby collieries was lifted into the atmosphere by very strong updrafts. Later on it fell back down to earth with hevy rainfall. It is possible that a small tornado could have been involved (but I have not heard of any reports of tornadic damage from that day).