Temperatures are to return to normal summer averages this week - but some areas could be hit with "thundery showers".
Met Eireann is predicting highs of 19C on Monday with some sunny spells expected in the south, east and midlands.
And Friday and Saturday could be even warmer, with the weather chiefs saying temperatures could hit the "low twenties".
However, there is persistent rain forecast for Tuesday, and northern and eastern counties may experience thunderstorms on Wednesday.
A forecaster said: "Dry at first tomorrow, Tuesday, but becoming increasingly cloudy through the afternoon. Patchy rain and drizzle affecting western and northern areas in the morning will turn persistent at times through the afternoon.
"The rain will slowly push eastwards by the evening but will tend to break up, with parts of the east and south holding dry for the day.
"Highest temperatures of 12 to 17 degrees Celsius in light westerly breezes.
"Tuesday Night: Mostly cloudy with outbreaks of rain at times.
"Overnight lows of 9 to 11 degrees Celsius in many areas but falling to 7 or 8 degrees Celsius in northern counties towards morning as skies clear and a northwest breeze sets in."
They added: "Wednesday: Rather cloudy and cool on Wednesday with northwest to northerly breezes.
"Some patchy rain in places Wednesday morning but brightening up with some sunny breaks developing but there will be heavy possibly thundery showers also especially in northern and eastern counties later in the day.
"Afternoon highs of 13 to 17 degrees Celsius."
Met Eireann is predicting changeable conditions throughout the week but it says the weather will get milder towards the weekend.
A spokesman said: "There is some uncertainty, but latest indications suggest it will become milder during Friday and Saturday with mostly east to northeast breezes and afternoon highs in the high teens or possibly low twenties in parts of the northwest but cooler near eastern coasts.
"There will be some showery rain in eastern counties with the potential for some thundery downpours."
