Update 7.43pm: Met Eireann have said that the arrival of tropical Storm Helene signals the start of a "very active period of weather this week".
The forecaster today issued a yellow rainfall warning for Galway and Mayo which is valid up to midnight tonight.
They have said that heavy rain is continuing in parts of Connacht and West Ulster along with fresh to strong winds.
However, elsewhere will see intense bursts of rain which may bring some spot flooding tonight.
They have said that most of the rain will clear by early tomorrow morning, but the unsettled weather will continue for the rest of the week.
Met Eireann said: "A very active period of weather is now expected to follow over the coming days with an assembly line of low-pressure systems swinging close to our shores, bringing strong winds and heavy rain at times.
"There is potential that wind or rainfall warnings will be required in at least some parts of the country over the next few days associated with these Atlantic low-pressure systems."
AA Ireland is warning motorists to exercise additional caution in the coming days as large amounts of rainfall are expected as the remnants of tropical Storm Helene pass over Ireland.
The warning to motorists came after Met Eireann extended a Status Yellow – Rainfall warning to five counties, Galway, Mayo, Sligo, Leitrim and Donegal, which will remain in place from 1pm today until 5am tomorrow.
AA Ireland is calling on drivers in the affected counties to adapt their driving to suit the weather conditions and to be on the lookout for vulnerable road users such as cyclists and pedestrians as visibility could be reduced during heavy rain.
"The expectation with this storm, according to Met Eireann, is that we will have a large volume of rainfall in quite a short space of time meaning that the risk of flooding in the affected areas is quite high," said Conor Faughnan, AA Director of Consumer Affairs.
"When you combine this with the lengthy, mostly dry spell of weather we’ve had recently motorists can expect roads in the affected areas to be significantly more slippery meaning that slowing down and slowing extra distance between yourself and other road users, especially vulnerable road users such as cyclists and pedestrians, will be vital.
"Driving in heavy rain is something that motorists across the country are well practiced in and ultimately it does not appear that Helene will bring weather conditions anywhere near as serious as what parts of the country saw last year with Ophelia.
"That said, however, we can’t get complacent where road safety is concerned so it’s important that motorists adapt their driving to the conditions."
With a significant risk of flooding expected, particularly in the west of the country, AA Rescue, the motoring organisation’s breakdown assistance provider, is expecting a spike in breakdown callouts as flood water often pose a danger to a car’s electrics and the engine.
"Where possible motorists should avoid driving through flood water but if you have no alternative remember to drop your speed and use a lower gear to help protect your car.
"We would also encourage motorists who do break down in the coming days to keep the bonnet closed while you wait for assistance if it is raining heavily. Leaving the bonnet open could make the engine significantly more difficult to start when assistance arrives."
Update 7.53am: Met Éireann is warning that several parts of the country could be hit by flooding today as Storm Helene makes its way towards Ireland.
Up to 40mm of rain is expected to fall.
A yellow rainfall warning has already been issued for Galway and Mayo which is valid from noon to midnight tonight.
Between 25 and 40 mm of rain is currently forecast to fall on the counties with a risk of flooding in places.
Many other counties are expected to be hit by heavy rain tonight.
Met Éireann says it is possible that yellow level warnings may be issued for Cork, Waterford, Wexford, Wicklow, Dublin, Meath and Louth.
Good morning all! 🌅
A mild start to the new week with temperatures later between 17 and 25C for most, but tonight #StormHelene will bring the first bout of several windy spells that we'll see this week 🌬️ @bbcbreakfast pic.twitter.com/Cl6NwFovXo— Matt Taylor (@MetMattTaylor) September 17, 2018
Current forecasts show south to southeast winds will reach gale or strong gale force at sea but will be fresh to strong over land as the ex-tropical storm tracks northeastwards close to the southeast tonight.
Rain will spread eastwards quickly across the country and will be heavy in many areas for a time with a risk of spot flooding.