There are reports of widespread localised flooding across Northern Ireland after heavy downpours of rain.
Police say the Clooney road near Greysteel and the Ballystockard road between Comber and Dundonald are badly affected.
The Knock dual carriageway in Belfast between the Castlereagh road and Newtownards road is also flooded.
They are advising motorists to take care and allow extra time for their journeys.
Winds of up to 60mph and heavy downpours hit the UK overnight as a deep low pressure tracked the country.
The Met office has issued a series of severe weather warnings, including for Northern Ireland, Wales, the west coast of Scotland and much of south-west England.
After the Indian summer of last week and the particularly unsettled conditions blow through Sunday, temperatures will return to seasonal norms this week.
Forecaster Rob Hutchinson, from MeteoGroup, the weather division of the Press Association, said the change would be a "shock to the system" after last week's sunny weather.
He said: "There's a rapidly deepening area of low pressure tracking across the country, and it is bringing a lot of heavy rain and strong winds.
"At the moment, it's the west mainly affected, but the heavy rain will transfer east through the day."
This week will see daytime temperatures return to single digits in much of the country, falling as low as 2C in some areas.
"It will be a shock to the system after last week's conditions," Mr Hutchinson said.
© Press Association