"In the six-hundredth year of the life of Noah, in the second month and on the seventeenth day of that month, all the fountains of the great deep were opened up; and the floodgates of the heavens overflowed exceedingly and filled all the face of the earth; and the waters prevailed beyond measure." So we read in Genesis, Chapter 7 - and the description could also aptly be applied to events in Dublin on this day 35 years ago. It was the occasion of the most dramatic thunderstorm ever to affect our capital city.
The downpour occurred on June 11th, 1963, and was associated with a prolonged but very localised outbreak of heavy thundery rain in the southern suburbs of the city. The most severe flooding occurred in the triangle bounded by Dundrum, Blackrock and Sandymount. Since there was no official rain-gauge in that immediate vicinity, the experts took the unusual step of appealing in the newspapers for any rainfall readings that might have been made by private individuals.
Many replies were received and followed up. Some of the observations were fortuitous - cases, for example, where people had noticed a can, a bucket, or other receptacle to be empty in the forenoon, and to contain a sizeable amount of water when the rain had stopped. By making the relevant calculations based on the dimensions of the container, it was possible for this amount of water to be translated into an equivalent depth of rainfall. It might not meet the criteria of the most stringent climatologists, but the method gave approximations of acceptable accuracy nonetheless.
But the luckiest outcome of the search was the discovery that a Mr Coleman of Mount Merrion had a proper standard rain-gauge well sited in the middle of his lawn. Aware of the unusual nature of the event, Mr Coleman had taken readings from his gauge at hourly intervals, and the researchers were presented with a perfect record of the rainfall at the very centre of the storm. It transpired that the total rainfall for the day in Mount Merrion had been 184 millimetres - more than seven inches - of which 80 mm, or three inches, had fallen in the single hour between two and three o'clock in the early afternoon.
It is possible, of course that even heavier rain has occurred in Ireland from time to time, but passed into oblivion undocumented. Many spectacular falls over the years may have escaped the notice of any conscientious Mr Coleman, their torrential nature evident only to those unfortunate enough to have been caught beneath them, or to have become victims of the flooding which undoubtedly ensued.