The highest wave ever to hit these shores has been recorded, according to Met Éireann.
The 67-foot wave was measured at a special buoy off the Donegal coast today as a force ten storm raged across the north coast.
Meteorologists at Met Éireann said data from the sea conditions about 60 miles to sea were the most severe it has encountered that distance offshore.
"At 2pm today the M4 weather buoy off the Donegal coast recorded a maximum wave height of 20.4 metres which is the highest maximum wave recorded in Irish waters," Met Éireann reported.
At Malin Head, the northerly most tip of Ireland, wind gusting to 140km/h was recorded.
Elsewhere, the Coast Guard has urged people to stay off exposed coasts, cliffs, piers, harbour walls, beaches, promenades during this week's forecast stormy weather.
Winds and stormy conditions will ease tonight before freezing conditions hit Ireland on Thursday and there is a risk of a second storm hitting the south and midlands. Forecasters, however, said there is a chance the storm may miss Ireland to the south.
The Weather Buoy project is a collaborative project between the Department of Transport, Marine Institute, Met Éireann and the UK Met Office.
Manager of the Coast Guard, Declan Geoghegan said: "The combination of tides, forecasted gale warnings for the next day or so, high sea conditions and swollen rivers may result in very dangerous conditions."
Noel Brett, CEO, Road Safety Authority said: "I would ask each and every road user to use the roads safely over the coming week.
"With bad weather forecast, we need to be prepared for these severe weather conditions of stormy winds, patches of ice and snow showers.
"Visibility for road users is severely decreased in such weather conditions, which increases the risk of collision.
"Therefore motorists need to drive safely and slowly, and all pedestrians, cyclists and motorcyclists should wear high visibility clothing to give them the best chance on the road."