Temperatures in parts of the country aren't expected to exceed 5C.
Met Éireann has issued a status yellow warning for heavy rainfall in five counties.
Dublin, Louth, Meath and Wicklow were all placed on the warning at 2pm yesterday, while it was expanded to include Kildare as well at 9pm.
The five Leinster counties have been drenched over the past 12 hours, and there's more to come — the weather warning will remain in place until at least midday on Wednesday.
The updated alert warns of "Further heavy showers or longer spells of rain will lead to rainfall accumulations of 25 to 35mm."
Motorists have also been advised to be cautious through the period of treacherous conditions.
Drivers in the affected areas are being asked to reduced their speed and watch out for the possibly of aquaplaning.
Met Éireann has forecasted that today will be "Cold & showery today. Some longer spells of heavy rain in East at times with some hail/thunder & local spot flooding. The best of the drier weather will be in South-West."
