Parts of Northern Ireland could be affected by flash flooding today as up to 30mm of rain falls in just a few hours.
Plummeting temperatures and chilly winds are expected, along with gusts of up to 50mph in some places.
The Met Office last night issued a yellow warning and weather experts predicted that heavy rain will batter most of the province from 8am.
MeteoGroup forecaster Tom Tobler said the combination of wind and rain would make for some miserable conditions throughout the day.
"There is a yellow warning in place for rain between 8am and 8pm, so it could be most unpleasant," said Mr Tobler.
"It will feel much colder than Sunday, but the main thing is it will be very windy with very heavy rain, starting in the west.
"It will clear eastwards in the afternoon but then showers will follow in behind that as well."
In other parts of the UK cold winds, frost and even some snow are forecast this week, signalling the end of the so-called October heatwave.