A weather warning has been issued for 11 counties and up to 50 millimetres of rain is expected in places.
The status yellow rainfall alert comes into effect at 9pm tonight for 24 hours and it is likely to cause some localised flooding.
The warning covers all of Connacht and counties Longford, Louth, Westmeath, Meath, Cavan and Monaghan.
All parts of the country can expect heavy rain overnight with the heaviest and most persistent across the west and north midlands.
Tomorrow morning will be wet and breezy across the country.
Heavy outbreaks in the northern half of the country will bring a continued risk of flooding.
In the south, the rain will become more intermittent but there will still be heavier showers at times.
Outbreaks of rain will continue in many areas on Tuesday night.
Frost will set in quickly after dark in the northwest where there will be lows of between -2C and 1C in north Connacht and Ulster.