A 14-year-old girl was one of eight pilgrims treated for hypothermia as thousands of people tried to climb Croagh Patrick despite safety warnings.
Reek Sunday pilgrims insisted on making an ascent of the country's holiest mountain, despite the event being officially cancelled due to appalling weather.
Eight people were treated for hypothermia on the slopes, including the teenager.
Members of Mayo Mountain Rescue expressed frustration at those who ignored their advice not to make the pilgrimage as it was considered dangerous.
"It's very frustrating when people ignore our advice not to attempt the journey up the mountain," said Ruth Cunniffe of the Mayo Mountain Rescue.
"There were hundreds of people who at least visited the mountain on Sunday, but we don't have confirmed figures on how many trekked up Croagh Patrick."
Despite repeated warnings not to proceed, a steady stream of people continued with their annual trek, including families with young children.
"Among the people who ignored our safety warning were a family with a 12-week-old baby, which is absolutely crazy," said Ms Cunniffe.
"We know the area well, and people should take our advice when we warn them not to make the journey.
"Even the local parish priest moved location in an effort to prevent people from hiking up the mountain."
Part of the temporary structure put up for masses on the top of the mountain was blown away, as was Mayo Mountain Rescue's medical tent.
The pilgrimage was cancelled at 7am yesterday, with masses moved to the nearby St Patrick's Church in Lecanvey.