Among them were customers at the Salt House Bar in Galway, who were celebrating when something out of the ordinary happened.
"I was cleaning up glasses and felt a drip on my head and we noticed that it was raining from the roof," said Liam McEvoy, who was working in the bar.
He went upstairs to the storeroom and discovered a keg had burst.
"When 20 litres of beer comes out of the keg there's a lot of it, so it spread across the floor upstairs and started to come through in a few different spots," he said.
Liam said staff cleared up the spill pretty quickly, but that did not stop some of the beer from raining down on customers in the bar.
"It was unfortunately just over two tables of girls, so we just gave them umbrellas and let them get on with their day," he said.
"At first everyone was a bit unsure what was happening, but it was St Patrick's Day so nobody was really going to complain or go home and they got a bit of a laugh out of it, getting served with umbrellas up in the pub even if it's bad luck.
"I think beer from the roof was strange enough, let alone having superstitions."
Eventually the drips subsided, but the female drinkers had got quite used to the novelty of using umbrellas indoors.
"I think the girls started to enjoy it so they kept them up for about half an hour, even though they probably only needed them for a few minutes," he said.

Police Sgt Nicholas Peacock told Mr Cipriani's trial he "appeared to be drunk" when he was brought into Hammersmith police station last June.
He was breathalysed and found to be nearly twice the drink-drive limit in June last year, his trial heard.
The 28-year-old's defence have argued the case should be thrown out.
They told Westminster Magistrates' Court there was a "lack of evidence" against the Sale Sharks star, who denies drink-driving in Fulham, west London.
Sgt Peacock told the court Mr Cipriani's eyes were glazed and "he smelt of intoxicating liquor, appeared to be drunk to me, and was upset and tearful."
More on this story and other news from London
The court previously heard claims police gave Mr Cipriani special treatment and delayed breathalysing him in a move the rugby player believed was "calculated to assist him".
Mr Cipriani was breathalysed after crashing his Mercedes into a taxi and found to have 67 micrograms of alcohol per 100ml of breath - nearly twice the drink-drive limit in England and Wales of 35 micrograms.
But Sgt Peacock said delays are common, particularly at shift changeover, as was the case when Mr Cipriani was brought in.
He also said the sports star was kept outside in a part of the station precinct known as "the cage" in order to stop other detainees recognising him.
"The concern is that if you have a well-known person and they are seen by other people, that information can potentially be leaked to the press," he said.
Philip Lucas, defending, told the court there was not "sufficient" evidence the breathalyser test in the police station was working properly and called for the case to be dismissed.
The move came after the prosecutor and district judge raised concerns that legal proceedings were being "filibustered" and the case "derailed" by "unnecessarily complicated" legal submissions made by Mr Lucas.
The case was adjourned until Friday.
Irish people around the world raised a glass or two in honour of their patron saint on St Patrick's Day.
[NEXT_CONCEPT]
England rugby star Danny Cipriani was "tearful and upset" after he was arrested on suspicion of drink-driving, a court has heard.