Met Éireann has issued a severe weather warning for tomorrow, with very high winds expected and possible flooding in coastal areas due to high sea swells.
Heavy and persistent rain in the west early in the morning will extend eastwards throughout the day, with clearer, showery weather later in the afternoon and evening.
The national forecaster said southerly winds, later veering west, would reach speeds of between 65 km/h and 85 km/h with gusts of up to 140 km/h.
The highest gusts will be along exposed coasts, and over high ground.
Rainfall totals of between 20mm and 30mm are possible over much of Connacht, west Munster and west Ulster, with totals of 15mm to 20mm elsewhere, Met Éireann said. Some flooding is likely.
The meteorological service said very high seas of some eight to 10 metres over the open sea may cause additional flooding in exposed coastal areas. The weather warning is in place from 9am to midnight tomorrow.
Sunday is expected to be cold and breezy, with sunny spells and scattered wintry showers, although the east of the country will have only a few showers.
“There will be little change on Sunday night but a widespread sharp ground frost will set in as southwest winds moderate. Monday will be a very cold day, with freshening, westerly winds; wintry showers will affect the north and west but mostly sunny skies are likely elsewhere,” Met Éireann added.
Next week is expected to be extremely cold, with sharp groundfrost setting in on Monday night, and wintry showers and the possibility of snow on Tuesday.
AA Roadwatch urged motorists to take particular care in the wet conditions tomorrow.
"In times of heavy rain, surface water can create very slippery driving conditions and additional precautions should be taken,“ said AA Roadwatch controller Nicola Hudson.
"At the very least, heavy rainfall will be a problem this weekend; motorists should reduce speeds accordingly and use dipped headlights to improve visibility.
“You will need to double the distance you leave between your car and the car in front of you, as braking distances are increased by wet roads.”
AA Roadwatch said motorists should also be mindful of more vulnerable road users including pedestrians, cyclists and motorbikes.
"Should you encounter flooding, the best advice is to avoid that stretch of road entirely. However if you decide to proceed, keep your engine revs high and speed low and go slow enough to avoid drowning the electrics or loosing grip. After passing through particularly deep water, test your brakes to make sure no damage has occurred."
The motoring organisation said the advice was pertinent to anyone travelling the west this weekend for the Galway International Rally 2009, where up to 15,000 people are expected to attend each day on routes throughout Galway county.
Irish Ferries said that due to the predicted weather conditions tomorrow, the cruises ferry sailing due to leave Holyhead at 2.10pm will depart at 1.30pm.
Further information is available on the company’s website and on its 24-hour pre-recorded telephone line at 0818 300 400.
Stena Line also urged intending passengers to check details of ferry sailings.
Further information for those travelling to Britain is available on the 24-hour phone line at 01 2047799, and at 44 (0) 8705 755 755 for those travelling to Ireland or Scotland.