The rainfall early yesterday was a rare event but not unprecedented, according to Met Éireann. The record for the State’s greatest deluge still dates to 1963 when three times more rain fell over a similar period.
Yesterday morning’s rain was very rare for such a high volume in a short period of time, according to Liam Keegan, head of Met Éireann’s climatological and observations division.
“Dublin airport got the heaviest rainfall in one hour since records began there over 60 years ago,” he said. Between 4am and 5am, 26.7mm of rain fell at the airport.
“There’s a one in 35 chance of that happening in any given year,” Mr Keegan said. Some 36.5mm of rain fell between 3am and 5am at the same location. “There’s a one in 55 chance of that happening.”
Those figures are dwarfed by events in 1963 when 83mm of rain fell in just over one hour.
“That was a real humdinger,” Mr Keegan said. “That puts everything in context.”
In Northern Ireland, the greatest hourly total of rain was in August 1980 when 97mm fell at Orra Beg in Co Antrim.
In contrast, 1887 was the State’s driest year on record, when just 356.6mm of rain for the entire year was recorded at Glasnevin in Dublin.
According to Met Éireann records, the greatest daily total rainfall occurred on September 18th, 1993, when 243.5mm fell at Cloore Lake, Co Kerry.
Mr Keegan said Dublin appeared to have felt the brunt of the deluge yesterday morning. It also felt the brunt of a similar torrent of rain on August 9th last year. Some 76.2mm fell in one day in the Dublin region.
“[The rainfall on] August 9th was over a prolonged period of time but this morning’s rain was over a very short period. Most of the rain fell between 3am and 5am.”
As recently as June 23rd, an area along the coast of Donegal experienced rainfall of up to 60mm in a four-hour period. Met Éireann said amounts in excess of this may well have fallen in a few locations.
