Met Eireann has issued a Status Orange rain warning for five counties from 10 pm tonight until midnight on Thursday..
Cork, Kerry, Waterford, Wicklow, and Wexford are among the counties affected by the alert.
Met Éireann forecasts heavy rain tonight and tomorrow, with thundery downpours and isolated floods possible. The national weather agency predicted disruption.
This week, eight counties will also be under a Status Yellow rain warning. The warning is in effect from 10 p.m. tonight until 10 p.m. tomorrow in Carlow, Kilkenny, and Tipperary.
Residents in these areas should prepare themselves for heavy rain tonight and tomorrow, with thundery downpours possible, which might cause localised floods and some disruption.
Cavan, Dublin, Kildare, Louth, Meath, and Monaghan have received a separate warning, which goes into force at 4 a.m. on Wednesday and lasts until midnight on Thursday.
Cork saw major flooding over the weekend as a result of excessive rain.
Cork City Fire Brigade and Cork City Council members worked all night yesterday to drain water from the city and keep flooding to a minimal.