Two weather warning have been issued for western and northern counties.
A status yellow rainfall warning is in effect for Connacht, Donegal, Clare, Cork, Kerry and Limerick.
Met Éireann is forecasting heavy and persistent rain overnight Wednesday through to Friday morning.
This will lead to some flooding and disruption, with accumulations of 30mm to 60mm expected.
There will be more rainfall likely in mountainous regions.
Howling Halloween👻🎃🪦:
Very unsettled across Ireland this week.The disturbed weather pattern is expected to persist for the Halloween weekend. Weather warnings at https://t.co/ozrQHtoOkt
View our Meteorologist's commentary here :https://t.co/ktXtWjbfIg pic.twitter.com/niqJPuDBJk— Met Éireann (@MetEireann) October 27, 2020
While a status yellow wind warning has been issued for Galway and Mayo.
There will be strong southwest winds on Thursday, with mean speeds of 55 to 65km/h and gusts to 100km/h.
The wind will be strongest in western parts.
Alan O'Reilly from Carlow Weather told Breakfast Briefing there is potential for a quickly-developing storm on Friday.
"It's a very wet morning out there and unfortunately it's going to stay very wet for many parts - especially in the west, where the risk of flooding is going to increase.
"Some very heavy rain this morning - and while it will ease in the south and the east later on through the day, it will continue in the west and the north.
"So you're looking at up to 60mm of rain expected between today and tomorrow.
"The wind's also obviously increase as well - there's a yellow wind warning for Galway and Mayo which comes into effect at 10 o'clock this morning."
"It will improve a little bit then for Friday, there'll be a bit of a break - the winds will ease and some early morning rain will clear to some sunny spells.
"But very interesting then, the weather models are struggling with potential for a very quickly-developing storm to arrive on Friday night and Saturday with a risk of some very strong winds.
"But the exact track of that system, even this close, is still not certain.
"But it does look like there will be at least a risk of some very strong winds for a time on Friday night and Saturday.
"And also then another spell of rain unfortunately on Saturday - so it does look like maybe it's just as well we won't be out trick or treating with a very wet and potentially very windy day on Saturday.
"And Sunday unfortunately does look like it's going to continue to be very windy".
However, the weather is set to improve early next week.
Alan explained: "The good news is is does look like high pressure is going to develop early next week, actually.
"So while we have a very unsettled spell of weather for the rest of this week and the weekend, it does look like the weather models are in fairly good agreement that the weather will settle down next week.
"It will turn cooler with that, though".
