It has been the coldest day since 2010 across Met Éireann's network of synoptic weather stations, according to provisional figures from the forecaster.

Met Éireann said that temperatures dropped to between -1C and -5C in most places last night, with Athenry, Co Galway recording -7.2C.

At the weather station in Ballyhaise, Co Cavan a maximum temperature of -3.1C was recorded throughout the day.

The lowest temperature of the year on the island was recorded in Katesbridge in Co Down, with a low of -9C seen in the early hours of this morning, according to the UK Met Office.

Met Éireann has warned of hazardous driving conditions as a result of severe frost, icy conditions and freezing fog. A Status Orange freezing fog warning elapsed at midnight.

The warning was issued for Connacht, Carlow, Dublin, Kildare, Kilkenny, Laois, Longford, Louth, Meath, Offaly, Westmeath, Cavan, Donegal, Monaghan, Clare, Limerick and Tipperary.

Freezing fog will be dense in places leading to "very hazardous" driving conditions, Met Éireann said.

The UK Met Office has issued weather warnings for ice and fog which will remain in place until 10am tomorrow, with sub-zero temperatures set to continue until later in the week.

Met Éireann has also issued a Status Yellow low temperature and ice warning for Ireland, valid until midday on Friday 16 December.

It has warned of widespread sharp to severe frosts with some showers of hail, sleet and snow, mainly near coasts, and freezing fog at times.

Met Éireann said low temperatures could lead to treacherous conditions on paths and roads, travel disruption, burst water pipes, and damage to engines. It also said there are increased risks to vulnerable members of the community.

The National Emergency Co-ordination Group met this afternoon and will meet each day this week to monitor the situation.

A statement from the group said that most schools remain open but a small number of schools were closed today due to hazardous local conditions.

Milder conditions were expected to return at the weekend, it said, adding that public transport is running but may be a bit slower than normal in some areas.

"Local authorities' severe weather assessment teams are continuing to monitor the situation and co-ordinate their responses. Widespread gritting will continue, as well as ploughing where necessary," it said.

Public urged to take care around open water during cold snap

The Coast Guard, RNLI and Water Safety Ireland have issued a joint water safety appeal urging people to be aware of the added danger around water during the cold spell.

In England, three boys died after being pulled from an icy lake in Solihull yesterday.

"Due to the freezing temperatures, many inland bodies of water have frozen over at canals, lakes, ponds and flooded areas. As the thickness of this ice can vary greatly the strong advice is to stay off the ice," said the statement from the Coast Guard, RNLI and Water Safety Ireland.

"Be extra vigilant while walking beside bodies of water as walkways and paths can become extremely slippery and unsafe when icy. Keep pets and young children away from the edges."

The statement added that cold water swims are very popular in the run up to Christmas and New Year.

They are advising people to take adequate care to acclimatise to the water before entering and to take extra care to warm up after swimming.

Water Safety Ireland's Deputy CEO Roger Sweeney said: "Children are naturally curious about walking on ice but parents should emphasise that it is not safe as the thickness can vary."

Members of the public are advised to dial 999 or 112 if they see anybody in trouble on the water, or use Marine vhf Radio Channel 16 and ask for the Coast Guard.

Full resources being used to keep public transport running - Minister

Meanwhile, Minister for Housing Darragh O'Brien said the full resources of the State are being used to try and keep public transport going and schools open.

Speaking on RTÉ's Morning Ireland, Mr O'Brien urged caution on the roads over the next few days and asked people to be aware of elderly or vulnerable neighbours.

He said there is "a stable energy supply" and they are "well in control of the situation".

Regarding schools, the minister said that while there will be discretion at a local level, the plan is to keep schools open.

Speaking on the same programme, Met Éireann's Gerry Murphy said there is "widespread frost" right across the country with icy patches in places.

Major roads have been well gritted, he said, but care will be needed on secondary roads.

He said counties in the northwest, such as Donegal, Mayo and parts of Galway, have had wintry showers.

Mr Murphy said: "The places that get to 4C will be along coasts, so really for much of the country the temperatures will stay down around 0 or 1C.

"That's the way it’s going to continue really right throughout the week, so it’s a very cold week in store."

Travel disruptions

Road Safety Authority Communications Manager Brian Farrell said motorists should heed any warnings on road closures during the cold weather.

Speaking on the same programme, he said that people should be aware of local or national weather updates and advice from gardaí and local authorities on road closures and treacherous conditions.

He said: "The emergency services have a lot to deal with, with weather conditions like this and situations like this.

"And the last thing you need to do now is to get yourself stranded or in a situation where they are having to divert their resources to maybe rescue you from a situation you probably shouldn't have got yourself into in the first place."

Mr Farrell said the advice has not changed in relation to how people should drive if they are on the roads during icy weather, and they should slow down, leave a gap to the car in front and avoid any sudden and harsh steering or braking.

Fog and ice: People braving the cold for some exercise on Friday in Co Kildare

Iarnród Éireann said there were delays on the Dundalk and Drogheda commuter services to Dublin due to weather conditions.

In Dublin, Luas Red and Green Line services are operating with delays and commuters are advised to allow extra time when travelling. The operator apologised for any inconvenience caused.

Dublin Bus said there were some curtailments on three routes this morning.

It said route 44b would not be serving Glencullen, the 47 would not be serving Belarmine and the 65 route would not be serving Ballyknockan.

Gardaí say care is needed on some secondary roads, where patchy ice could make driving conditions dangerous.

More than 70 flights cancelled at Dublin Airport

Meanwhile, over 70 flights in to and out of Dublin Airport were cancelled today due to the weather.

A daa spokesperson said 41 outbound flights and 32 inbound flights were cancelled "mainly due to poor weather conditions at UK airports"

They added that runways and taxiways at the airport are currently being pre-emptively sprayed, given the potential for sleet this evening.

The departing flights included Aer Lingus and British Airways services to Leeds Bradford, Heathrow, London City and Birmingham, while the cancelled inbound services from those airlines are from Heathrow, London City, Donegal, and Birmingham.

There are also cancelled Delta Airlines services to and from the US city of Boston.

Shannon Airport is also reporting eight total cancellations.

The affected routes are Aer Lingus services to and from Heathrow as well as Ryanair services to and from Gatwick and Stansted.

There are some flight delays at Cork Airport, but no cancellations as of yet.

Aer Lingus said it is experiencing challenges with its London Heathrow operation due to freezing fog conditions there and has cancelled some flights from the airport.

On its website, the company also advised customers travelling to London Heathrow to expect delays on the services that are operating.

Some of its UK regional services have also been cancelled.

Aer Lingus said it continues to monitor the weather conditions in the UK and passengers due to travel can check the status of their flight on aerlingus.com.