'Precautionary' flood prevention measures are in place in east Belfast amid flooding fears at high tide on Saturday.
Disaster was averted in the area earlier this month, when the predicted tidal surge failed to breach defensive barriers of some 40,000 sandbags.
Some parts of Co Down have already suffered the effects of rainfall, with several roads closed for a time in areas such as Newcastle.
Sinn Fein MLA Chris Hazzard was among those on the ground helping residents affected by flooding.
He said the area had suffered "extreme flooding", with water entering some houses.
According to Meteo Group forecaster John Griffiths, up to 24mm of rain fell in parts of Northern Ireland in just six hours on Friday morning.
"There has been very heavy rainfall, with 24mm in some areas from 6am on Friday," he told the Belfast Telegraph.
"That would be very high for this period and we've already had a lot of rain over the past few days."
Video report showing flood defences in east Belfast earlier this month
The highest levels were reported just outside Draperstown in Co Londonderry.
He said while rain would ease off on Friday evening, Saturday was set to bring yet more showery weather.
"There is a risk of flooding with more high rainfall saturating the ground."
A yellow warning for heavy rain has already been put in place by the Met Office.
In east Belfast a high tide at 11.54am on Saturday could bring flooding to the area.
But according to the Rivers Agency, early indications predict the surge is not expected to be of the same scale as that which occurred earlier this month.
"The most critical tide will be at 11.54am. In addition, there has been a lot of rainfall recently, leading to saturated ground and high river levels," said the agency's Pat Aldridge.
"Further rain is forecast and therefore there is a risk of river and surface water flooding, particularly if high flows coincide with high tides."
Victoria Park will also be closed on Saturday as a result of the high tide.
Meanwhile, Ballymena RFC's clash with UCC has also been called off due to a waterlogged pitch.
The latest poor weather comes as parts of southern England have seen the wettest January on record, with more rain set to bring further misery to flood-hit areas.
A large area from east Devon to Kent and inland across parts of the Midlands has already seen twice the average rainfall for the month, figures from the Met Office show.
The rain has caused widespread flooding, with the Army being deployed to the Somerset Levels to bring relief to villages cut off by the most significant floods for 20 years.
The Met Office is warning of a band of heavy rain sweeping the country tomorrow, with 20mm to 30mm set to fall across many parts and as much as 40mm on high ground.
Over the weekend, winds of up to 50mph to 60mph are set to hit the country, which combined with spring tides could see western coastal areas battered by large waves.
The bad weather will worsen the problems faced by some areas such as Somerset.
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