Police in Northern Ireland are warning the public not to travel between 21:00 GMT on Monday and 09:00 GMT on Tuesday due to heavy rain warnings.
An amber warning for heavy rain will be in place between those times in counties Armagh, Antrim and Down.
The Department for Infrastructure (DfI) said it may be necessary to close roads or put temporary restrictions in place.
An amber warning is the second-highest level of alert, indicating an increased risk of flooding and disruption.
A yellow warning is currently in place for most Northern Ireland counties until noon on Tuesday.
Another yellow warning has been issued for heavy rain on Tuesday until 09:00 on Wednesday.
Further heavy rain is expected on Thursday as Storm Ciarán arrives.
“These warnings follow an extremely wet weekend where flooding has already occurred on many roads,” the DfI said.
“The persistent wet conditions on saturated ground and with higher river levels will inevitably lead to more localised flooding.
“Traffic disruption is possible and the public are being asked to consider their journeys and take extra care if travel is necessary.”
Rugby pitches at the Stormont estate after heavy rain
The department issued advice for motorists making essential journeys in flood conditions.
“If your journey is essential, reduce your speed, stay well behind the vehicle in front, remain focused and always wear your seatbelt,” a spokesperson said.
The DfI said its roads and rivers teams have been checking and clearing road gullies and drainage grilles and additional staff will be on standby.
“Monitoring of water levels and tides has been ongoing and will continue until the weather warnings have elapsed,” it said.
The Met Office is warning of between 25mm and 50mm of rain in places.
Up to 100mm is also possible over higher ground, with risks of possible flooding.
Homes and businesses could be affected, and travel disruption can be expected.
The Northern Ireland Fire and Rescue Service was called in to help rescue sheep from a field
The DfI warned drivers of the potential dangers of driving through floodwater.
“A half wheel depth of fast flowing water could move your car. Even driving through shallow water could damage your engine,” the DfI said.
In Dromantine, County Down, approximately 100 sheep were stranded in a flooded field on Monday.
The sheep are brought to dry land
About 70 were rescued by local farmers, with the Northern Ireland Fire and Rescue Service rescuing the remaining 30.
Assistant Group Commander Alistair McConville said they had been alerted by a local farmer concerned for the safety of his sheep.
Assistant Group Commander Alistair McConville warned farmers who had sheep in fields to get them to shelter or high ground
“Obviously we weren’t sure of the depth of the water going in there, so that’s why we had our special rescue team from Belfast who kept our firefighters safe and then our large animal rescue team from Newcastle who are specialists in dealing with animal rescues.”
He said that, with the weather warnings for more rain, if farmers have sheep in fields they should get them to shelter or high ground.
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The system will bring rain to Norther Ireland, especially towards the east.
A warning has been issued from 06:00 until midnight on Thursday.
The Met Office said rainfall would be likely to reach 20-30mm widely, with 40-60 mm accumulating across high ground.
It is the third named storm of the season after Storm Agnes and Storm Babet.
On Saturday parts of Northern Ireland experienced flooding, leading to road closures in County Down.
Elsewhere, part of the A2 Antrim coast road was closed on Friday after heavy rain led to a landslide between Glenarm and Ballygally.
In the Republic of Ireland, County Wexford was one of the worst affected areas, with up to 35mm of rain falling from late Saturday evening.
The National Heritage Park in Ferrycarrig, outside Wexford town, was forced to close due to flooding, just two months after it reopened following a €1m (£872,000) refurbishment.
Streets in Cork city centre were closed or partially closed on Saturday night due to tidal floods.
