Met Éireann has issued rain warnings for 20 counties.
The forecaster has warned of potential localised flooding, dangerous travelling conditions and reduced visibility in the areas as heavy rain expected and a chance of thunder.
A Status Orange alert is in place for Kilkenny, Wexford and Waterford until 1am tomorrow.
A Status Yellow rain alert is in place for Carlow, Dublin, Kildare, Laois, Longford, Louth, Meath, Offaly, Westmeath, Wicklow and Roscommon, also until 1am tomorrow.
A separate Status Yellow rain warning is in effect for Clare, Cork, Mayo, Limerick, Tipperary and Galway until 6pm this evening.
Rain will slowly move north-eastward across the country during the afternoon. Sunny spells and showers will follow in the south west.
Highs of 10 to 14 degrees are expected.
Gerry Murphy, senior forecaster with Met Éireann, told RTÉ’s Morning Ireland that the week ahead will be generally wet:
“Rain will tend to hang over north Leinster and Ulster as we go through this evening and tonight.
“Then once it clears, showers tomorrow but more rain pushing up from the southwest on Wednesday, some further rain in the south possibly tomorrow night and overall for this week, quite an unsettled picture with more rain on the way.”