Temperatures could dip as low as -3C overnight, forecasters have said.
People have been urged to be careful when out and about, while some sports fixtures have been postponed.
Belfast Zoo also shut this weekend, with the local council warning of some playground closures due to icy conditions.
One weather warning ended at noon, but the second one came into force from 3pm and runs to Monday.
People have been advised to be alert when out and about.
The PSNI said this afternoon: “Winter weather conditions are to continue over the weekend and we’re urging motorists to take extra care on the roads.
“Snow and ice are forecast throughout NI, and a yellow weather warning is in place until Monday.”
The Department for Infrastructure said: “Temperatures fell below freezing overnight and there is a risk of ice and snow on roads.
“A Met Office yellow warning of snow and ice for Northern Ireland is in place valid until 12 on Monday.
“Salting of roads on the scheduled network (including the deployment of snow ploughs on higher ground routes) took place overnight and this morning. Road users are advised to exercise caution when travelling, particularly when driving on untreated roads.”
The Saturday sporting programme was also affected as frozen pitches saw a series of games called off.
Winter weather in Co Armagh on January 2. Luke Jervis/Belfast Telegraph
One of the biggest casualties was today’s GAA clash between Tyrone and Fermanagh, which was postponed.
This afternoon’s NIFL Premiership clashes between Ballymena United and Glenavon, and Portadown v Cliftonville were also called off after pitch inspections.
Most of the Championship programme was postponed with five of the six games off – Ards v Limavady; Newington v Dundela; Loughgall v Ballinamallard; Queen’s University v Warrenpoint; and Annagh United v Institute.
Dergview v Knockbreda and Ballyclare Comrades v Newry City in the third tier were also called off.
People have been warned that the cold weather will last through the weekend.
The Met Office said wintry showers will become more widespread, and will likely bring some disruption to travel.
Winter weather in Co Armagh on January 2. Luke Jervis/Belfast Telegraph
A spokesperson said: “Snow showers will continue to affect many parts of Northern Ireland over the weekend, before gradually easing on Monday.
“The heaviest and most frequent snow showers will be in the north, although along the north coast these may fall as rain or sleet at times.
“Whilst not all locations in the warning areas will see snow, around 1-3 cm is expected to have fallen in many places by Monday morning, with the potential for 5-10 cm to build up in a few locations, especially over higher routes, such as Glenshane Pass. Ice will be an additional hazard for many.”
Snowy scenes on Cavehill Photo: Gareth Hanna for Belfast Telegraph
The spokesperson added: “All of Northern Ireland will remain bitterly cold over the coming days. Overnight lows are expected to dip to at least -2 or -3C, with rural spots potentially seeing even lower values.
“Daytime temperatures will generally reach the low to mid-single figures, but rural areas, especially those with higher ground or lying snow, may struggle to rise above freezing.”
The Met Office said there was potential for up to 10cm of snow in higher areas like the Glenshane Pass.
Cold weather is also causing problems in the Irish Republic.
A yellow alert for Co Donegal was in place from 8pm last night to 11am today, amid warnings of wintry showers “with some snow accumulations”.
A separate Status Yellow low temperature and ice warning was issued for several other counties.
Motorists were faced with blizzard conditions in Co Antrim on Saturday when heavy snow made the roads treacherous in the Carmavy area. Stephen Davison/Pacemaker
News Catch Up – Thursday 1 January
Meanwhile, the UK Health Security Agency (UKHSA) has issued warnings across England for the start of the year, which are in place until 10am on January 6.
The UKHSA said it means the weather is “likely” to cause significant impacts across health and social care services, including a “rise in deaths” among those with health conditions or aged 65 or over.
Met Office chief meteorologist Rebekah Hicks said: “Arctic air and brisk northerly winds are gripping the UK as we start the new year.
“Snow and ice warnings remain in force for many areas, with the risk of heavy snow showers, especially across northern Scotland and over higher ground elsewhere, though many inland areas will stay largely sunny and clear.
“Bitterly cold conditions will persist through the weekend and into next week, with daytime temperatures struggling to rise above freezing for some, and overnight lows dipping to minus double figures in places.”