A Status Orange weather alert for snow and ice comes into effect at 3pm today.
It will remain in place until 11am tomorrow when we'll get a fresh update from Met Eireann.
Two separate weather systems are at play. The Beast from The East is bringing bitterly cold conditions, while Storm Emma approaching from the south is expected to produce blizzard conditions.
So far it looks like Thursday will be the worst day.
We're already being warned by the Taoiseach not to make any unnecessary journeys.
Leo Varadkar is asking "people to pay close attention to any weather warnings and advice that's issued in the coming days. We'll either be asking people to stay at home and not make any unnecessary journeys, or if they're in work to stay there."
Business group ISME is reminding employers that they have "a duty of care for all employees under the Safety Health and Welfare at Work Act".
It is asking companies to consider if "it is safe to ask employees to travel to work, or to undertake their work."
Dubliners are being told the freezing weather will probably get worse as the week goes on.
The other counties affected are Kildare, Meath, Wicklow, Louth, Laois and Carlow.
The Dublin Regional Homeless Executive said there are "100+ additional beds available this week along with enhanced day services", for homeless people affected by the cold.
It’s expected schools will only close on a case-by-case basis depending on where the snow hits.
Homeless groups are warning of a potential risk to life with exceptionally low temperatures in the coming days.
The Dublin Region Homeless Executive, working with charities will ensure that those without a bed can access one, while the Peter McVerry Trust will be opening up a sports hall in Dublin 8 for extra emergency beds.
The Government's Emergency Co-ordination Group for Severe Weather meets later to discuss the forthcoming weather event, which is set to bring 'disruptive amounts of snow'.
Housing Minister Eoghan Murphy says rough sleepers will be prioritised.
"When we are doing our cold weather initiative we generally roll to a 24 hour service so that people are not forced out into weather conditions that are dangerous to their health and wellbeing."
Met Eireann's Pat Clarke says there'll be a 'very severe and penetrating frost by night. Values by day will struggle; we'll be lucky to get to zero degrees during Wednesday and Thursday.'