Irish folklore tells us this cold snap is the result of the tale of 'the brindled cow' or laethanta na bó riabhaí, as Gaeilge. 

This inclement weather during the first few days of April are a result of days being borrowed from March, according to a story which has been recorded in Irish folklore via The Schools' Collection of Dúchas.ie, a project which features approximately 740,000 pages (288,000 pages in the pupils’ original exercise books; 451,000 pages in bound volumes) of folklore and local tradition compiled by pupils from 5,000 primary schools in the Irish Free State between 1937 and 1939.

"One time a poor old cow got the better of getting over the month of March and she rose her tail over her back with joy. With spite on the cow March borrowed three days from April and the cow died. That is one of the reasons three first days of April are called Riabhach days."

From the Schools' Collection, on Dúchas.ie

In better news, these days are due to finish today, the third of the month. For more information on Laethanta na Bó Riabhaí, look here.