Wexford, Wicklow, Galway, Mayo, Cork, Kerry and Waterford have been warned of a Status Yellow rainfall.
A total of 25-40mm heavy and intense rainfall is expected, said Met Éireann and because of the heavy rain, localized flooding is also expected.
The alert is valid from 9 pm tonight to tomorrow midday, because the rain will clear the western counties by tomorrow early morning.
In other places, there will be slight drizzles today, importantly in the western and north western costal areas.
Clouds will rise from the west during the day and rain highs from 13 to -15 C in the afternoon across the Atlantic Ocean.
Tonight, the wet and windy areas in the west and southwest will become heavier and more stable, with the possibility of spot flooding spreading across the country.
The midlands and east will have a wet start tomorrow. Heavy rain will continue for a period of time and that will create the risk of spot flooding.
Sunny and clear weather with scattered showers in the west will gradually spread to all regions during the day at a temperature of 12C-15C.