Met Éireann has updated weather warnings to Status Orange for rain in counties: Donegal, Galway and Mayo.
The counties will enter into a yellow weather warning from 12:00p.m today (Sunday, August 4), along with the rest of Connacht and Co. Clare.
From 12:00a.m tomorrow (Monday, August 5), the Status Orange warning will be in place, with heavy rain continuing through the night, until the warning lifts at 10:00a.m on Monday.
Met Éireann has also said there will be strong and gusty southerly winds, especially in exposed areas during those times.
The national forecaster warned of flooding, difficult travelling conditions, and poor visibility.
It will be generally dry in the rest of the country, with patchy drizzle expected, along with mild and humid with temperatures, not falling below 13 to 17.
Through tomorrow afternoon, rain will track eastwards, with sunny spells and isolated showers expected in the east for the remainder of the day.
Met Éireann
Rainfall amounts are expected to range from 20mm in the southeast to 75mm in the northwest, which is between 120% and 210% of average across the country.
With persistent heavy rain, soil moisture deficits across all soil types are between 0 and 15mm in the northwest, with soils closest to the coast saturated.
Soils are drier elsewhere with moisture deficits of 20 to 65mm, leading to restriction to growth.
Wetter conditions in the week ahead will result in a reduction to soil moisture deficits in the west and northwest.
Soils in much of Connacht and Ulster will become saturated or waterlogged.
The national forecaster has also issued a potato blight advisory, affecting most of the country. The warning will come into effect from tonight until Tuesday (August 6).