The national forecaster has issued a Status Yellow rain warning for counties Donegal, Mayo, and Sligo, as heavy rain is predicted across many areas there today.
Elsewhere, the weather will remain largely dry until Wednesday, with just the odd shower breaking out. Temperatures will remain fairly mild, reaching 21C at times.
The weather is expected to take a marked turn for the worse on Thursday, as a band of heavy rain crosses the country. Friday is forecast to be a very wet and windy day, with gusts reaching speeds of 120-130 km/h.