Met Éireann has issued a rain warning for three counties in Munster, with localised flooding and heavy rainfall expected over the next 24 hours.
The status yellow rain warning affects Cork, Kerry and Waterford, with poor visibility and difficult travelling conditions in store for the affected counties.
The warning, which comes into effect at 1am on Monday night, will remain in place until 3pm on Monday afternoon.
The forecaster has predicted heavy showers of rain while the warning is in place, marking a stark change in weather conditions from earlier this week.
Last Friday was the hottest day of the year so far, Met Éireann has confirmed.
The forecaster says its weather station in Dublin's Phoenix Park recorded a temperature of 24C this afternoon, while its station in Mount Dillon, Co Roscommon, recorded a temperature of 23.7C.
Met Éireann has also issued a second weather warning, affecting those in Cavan, Donegal, Monaghan, Dublin, Kildare, Louth, Meath and Wicklow.
A Status yellow thunderstorm warning has been issued for these counties, bringing "heavy showers", mixed with thunderstorms and hail.
The adverse weather conditions may cause hazardous driving conditions and poor visibility.
The warning, which came into effect at 12pm on Sunday, will remain in place until 7.30pm on Sunday evening.
Weather conditions are expected to change again on Monday, with rain forecast for the coming days.
"Outbreaks of rain and drizzle will continue across the north and east for a time on Monday night," the forecaster said.
Tuesday will see a mixture of rain and showers, coupled with "sunny spells".
Maximum temperatures of 14C to 18C in moderate easterly winds are expected.
Later in the week, the forecaster predicts "changeable weather" with rain and showers at times along with some sunshine.
Check out the Irish Examiner's WEATHER CENTRE for regularly updated short and long range forecasts wherever you are. Rainfall and temperature charts are also available.