A weather warning for snow and ice has been issued across Northern Ireland as strong northerly winds bring arctic air across the UK and Ireland.
The Met Office alert began at midnight and will last until noon on Wednesday, with the organisation warning that commuters travelling over higher routes could face disruption.
While little to no snow is expected for most lower levels, 1-3cm is likely over high ground with some spots possibly seeing up to 5cm.
This could affect routes such as the Glenshane Pass and the Coleraine Mountain Road.
How cold will it get?
Ice is also likely on untreated surfaces with overnight temperatures falling to freezing and below quite widely.
The Met Office has also warned that hail and lightning will be additional hazards.
The weather warning for snow and ice is to last until noon on Wednesday [BBC]
The arctic air will bring temperatures down, well below average, both by day and by night in the coming days.
Highs between 3-6C are forecast on Wednesday and Thursday with the wind chill making it feel closer to freezing.
Sub-zero temperatures are expected on Wednesday and Thursday [BBC]
The average day time high at this time of year is closer to 10C.
Sub-zero temperatures are also forecast for Wednesday and Thursday night, leading to frost and a further risk of some icy patches.
Temperatures are expected to rise a few degrees closer to average over the coming weekend.
Met Éireann issues snow warning
A warning for snow and ice has also been issued for five counties in the Republic of Ireland from 00:00 local time on Wednesday.
The Met Éireann alert warns of hail, sleet, and snow with modest accumulations in places, especially over high ground.
The warning for Cavan, Donegal, Leitrim, Monaghan, and Sligo lasts until noon on Thursday.