Met Éireann has issued a status yellow rainfall warning for Connacht.
The warning came into effect at 12am Monday and will be in place until 6pm tonight.
Met Éireann said that "heavy or prolonged showers with the risk of thundery downpours could lead to rainfall accumulations of 25 to 40mm over the period."
The rest of the country will also see rain develop throughout the day, especially in the northern half of the country.
Occasional heavy thundery downpours are expected.
The forecaster says the showers will "become isolated" this evening and tonight "there will be long clear periods."
Temperatures to today will reach highs of 21 degrees with Wednesday seeing similar warmth.
Wednesday will be "a significantly less showery day".
However, Met Éireann warns that "any showers that do develop will be intense".
The good news is that spells of sunny weather will occur in the morning and early afternoon.