An Arctic blast of very cold air will this weekend bring snow, sleet, hail, freezing rain and icy conditions across most of the UK, forecasters have said.

The Met Office issued new yellow warnings for wintry conditions and potential travel disruption lasting until Sunday morning. Previous snow and ice warnings for Scotland and northern England expired at noon on Friday. Freezing temperatures have also led to a four-day health alert for cold weather.

In northern Scotland and coastal areas of north-east England and Yorkshire from 4pm until 10am Saturday there are warnings of snow, sleet and hail showers. Across Wales, south-west England, northern England, the Midlands, the east of England down to London the warning is for ice between 5pm and 10am on Saturday.

A yellow warning for ice has been issued for Northern Ireland, which will be in place from 8pm on Friday until 10am on Saturday.

A further snow and ice yellow warning comes into place between 9pm on Saturday and 10am on Sunday. It covers Scotland and northern England, with forecasters predicting potentially heavy snow and freezing rain.

The wintry conditions would mean hazardous ice on untreated roads and pavements, forecasters said. The Met Office said the wintry weather was the result of an Arctic maritime air mass bringing colder conditions from the north of Scotland southwards.

On Friday morning, National Highways said the A66, a major route across the Pennines, was closed between the A67 near Bowes in County Durham and the A685 near Brough in Cumbria because of “concentrated snowfall”.

It said: “National Highways area team crews are on scene with winter treatment vehicles working to clear and treat the carriageway, however forecasts predict that snowfall will continue in the area throughout the morning. Units from Cumbria police are also on scene assisting to clear the traffic. Road users travelling across the Pennines are advised to plan ahead and consider alternate routes.”

The UK Health Security Agency issued yellow alerts for cold weather across northern England and the Midlands from 6am on Friday until 8am on Monday. The alerts warn of a greater risk to life for vulnerable people and increased use of healthcare services by vulnerable people.

The wintry weather comes after a strikingly wet start to 2026 for large parts of the UK. People in parts of Devon, Cornwall and Worcestershire had rain for 40 days, the Met Office said this week. On Friday in England there were 76 flood warnings and 154 flood alerts in place. In Wales there were four flood alerts.

For others it was the absence of sun, with Aberdeen going through 21 days of sunless weather until, finally, it came out for about 30 minutes on Thursday afternoon.

Heathrow airport has revealed a crowding problem that a third runway cannot solve: British and foreign travellers walk on different sides, and keep colliding, according to its chief executive.

Thomas Woldbye said that while Heathrow serviced more passengers in a smaller overall area than comparable European hubs, part of the London airport’s trouble was the differing continental sense of direction.

Speaking at an industry event, the Danish boss said one reason people thought Terminal 5, the main terminal used by British Airways, was crowded was that people were “in the wrong place”.

In comments to the Aviation Club UK, he said: “The problem is that all the British people keep to the left and normally Europeans keep to the right. And they do that in both directions.

“So we can be crashing into each other, and I see that from personal experience.”

Woldbye said that while “I have jokes with our people”, it was an issue that could be changed. “We just need to make sure that everybody going this way keeps to the left and this way to the right. I know that’s simplified but that is the sort of thinking that we need,” he said.

Heathrow will build more satellite terminals should it succeed with plans for a third runway, which could add about 40 million extra passengers of varying directional preferences to the mix. The 240,000 extra flights a year will be guided by air traffic control.

Woldbye said even with expansion, backed by the government, rival international hubs would grow faster than Heathrow. “London will lose market share every single year for the next 10 years. I think that should be a serious concern,” he said.

Meanwhile, the airport is attempting to address concerns that a third runway is incompatible with the UK’s 2050 net zero goals by accelerating the use of sustainable aviation fuels (SAF).

It has established an £80m pot – paid from landing charges – to subsidise airlines that choose to use more SAF on top of the minimum required under national mandates.

The mix of aviation fuel in the UK must average at least 3.6% SAF over the course of 2026, but Heathrow expects to hit a self-imposed target of 5.6%, helping airlines to cover some of the additional cost of the more expensive cleaner fuel.

Planes running on SAF – so far largely produced from recycled cooking oil – emit equal amounts of CO2 in flight as those using fossil fuels, but the net carbon footprint is calculated as lower because of the “life cycle”, ie how it is produced compared with normal jet fuel. SAF is regarded as a potential solution to significantly decarbonise long-haul aviation, although many remain sceptical.

Matt Gorman, Heathrow’s director of sustainability, said: “We have looked to use our scale and influence to attract SAF and we’ve shown you can get SAF flowing. The next challenge is stimulating domestic production – from a carbon, but also a energy security and growth perspective.”

Duncan McCourt, the chief executive of industry group Sustainable Aviation, said government pledges to start building five UK fuel plants by 2025 had been “optimistic”, with none yet under construction, but added they were making progress. “There is a real economic growth opportunity, for tens of thousands of jobs in the UK by 2050,” McCourt said.

Provisional figures published this week showed that the 2025 supply met the UK’s first annual fuel mandate of 2% SAF, with high uptake in the final months of the year after fears that the industry would miss the target.

Heathrow has reported falling profits and a squeeze on passenger growth, as its boss said that slow progress on its “underestimated” £33bn third runway scheme should be a national concern.

Thomas Woldbye, the chief executive of Heathrow airport, said major decisions on its funding model and the legal underpinning for expansion needed to be taken by regulators and government this year if the airport was to meet the timetable set down by the chancellor, Rachel Reeves, for construction to start by 2029.

Heathrow expansion meant building “almost a whole new airport” in west London, he said, with a total £49bn being spent on adding and renovating terminals as well as the runway.

About 276,000 more flights a year could come with a new runway, expected by 2035 at the earliest.

“I think sometimes people underestimate what we’re doing here. We would like to be transparent,” said Woldbye.

“In terms of its physical impact it’s no different from what we’ve asked for 15 years.”

Woldbye said of the current restart of the project since Labour came to power: “Given the need for a third runway, we would have liked to see it progress faster on some decision points. The chancellor has set deadlines we want to meet [but] the planning process is not the most straightforward.”

He added: “If we are to write a cheque for £33bn we would want some safeguards.”

In a statement, Heathrow said that “to ensure it is fully privately financed, the Civil Aviation Authority (CAA) must put in place the framework that gives investors confidence.”

The landing charges that airlines pay to Heathrow are fixed by the CAA on a five-year basis, and airlines fear they could increase significantly to fund a third runway. But Woldbye said the airport was not seeking “wholesale change to the regime”.

A review of the Airports National Policy Statement, which gives legislative backing to the third runway, is also under way.

Woldbye said: “If we are going to meet the deadlines those decisions need to be taken this year.”

Passenger numbers would continue to grow by only “a relatively small amount because we are running out of space … that should be a concern for the country, limiting our growth,” he added.

Heathrow pre-tax profits, meanwhile, fell by more than a third to £575m for 2025, from £917m in 2024, partly due to lower landing charges and also to higher maintenance costs, as passenger numbers reached a record 84.5 million.

The airport paid £550m dividends to shareholders, who consist mainly of overseas investors led by private equity firm Ardian and the sovereign wealth funds of Qatar and Saudi Arabia.

Woldbye said that after a five-year pause “we felt with a really strong performance in 2025 and some cash generation it was the time to look to the shareholders”.

Anti-expansion campaigners pointed to Heathrow’s growing debt pile, which is approaching £19bn. Heathrow said that it was not a barrier to a new runway. However, Paul McGuinness, the chair of the No 3rd Runway Coalition, said it raised questions over financing.

“A government which supports the project will be committing the taxpayer to bailing it out – if it’s ever to be more than an unfinished hole in the ground,” McGuinness warned.