5 counties in particular have been included in the warning.
The State broadcaster has issued a rainfall warning.
The status yellow rainfall warning was issued at 9pm this evening.
The warning has been given for counties Donegal, Galway, Leitrim, Mayo and Sligo.
The warning promises heavy rain at times this afternoon and tonight, with falls of 25 to 40 mm expected and a risk of local flooding.
The warning is valid from Monday 17 September 2018 9pm to Tuesday 18 September 2018 at 5am