Britons are being told to prepare for wintry weather as a “polar maritime airmass” from northern Canada spreads across the country, bringing snow, ice, rain and freezing temperatures.

Weather warnings are in place across the whole west coast of Britain on Thursday, the whole of Scotland, and the whole of the south of England, with potential for snow showers, icy roads and pavements, the Met Office said. Scotland also faces strong winds, gusting up to about 60mph.

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Public Health England called on people to take action to stay warm, ensure they have stocks of food and vital medicine before the cold weather arrives, and to think about how they can help others with underlying health conditions and those aged over 65.

Prof Paul Cosford, director for health protection and medical director at PHE, said: “Keeping your home heated to at least 18C, wearing lots of thin layers instead of fewer thicker ones, and – if you have to head out – using footwear with a good grip, are all ways to deal with this weather and stay well this winter.”

Chief meteorologist Paul Gundersen said conditions would become increasingly cold and windy as polar air spreads south across the country, with widespread severe frosts and significant windchill.

“Wintry showers are also likely to affect many areas, most likely falling as snow over higher ground but occasionally also to low ground, especially where showers occur inland overnight,” he said.

“On Thursday, a band of rain spreading from the west across southern parts is likely to turn wintry during the afternoon, with the potential for heavy snow in places. As this clears through the evening, with clear skies there is a risk of a widespread frost and icy conditions quickly forming.

“With wintry weather expected across much of the UK, it’s a good idea to keep in touch with the latest forecast and our weather warnings.”

Met Office (@metoffice) ⚠️Stream of very cold air will affect much of the UK tomorrow with the risk of #snow for many ⚠️ pic.twitter.com/fC3uD3EJRH

The coldest urban temperatures on Thursday will be in Edinburgh, where the mercury will struggle to reach one or two degrees, according to Emma Sharples, a Met Office meteorologist.

Belfast is likely to be almost as cold, while Birmingham could reach 3C. The London area will be marginally warmer, at about 6C, and Plymouth could reach 7C although a “biting windchill” will make temperatures feel much colder, Sharples said.

Snow is possible as far south as London, as the wet weather mixes with cold air from the north.

“By the time we get through the course of [the day] the real cold air will have set in across all of the country and there will be probably be some snow lying in places as well,” Sharples said.

“Where there is a lot of snow we will get some quite cold conditions overnight, with very low temperatures. We could be looking at temperatures in the range of -5C to -10C in some locations away from towns and cities … in the north of England.” Further south could see temperatures falling to -5C, she said.

A polar maritime airmass was behind the bad weather, Sharples said. “That relates to where the weather is coming from,” she said. “Polar relates to where the air is coming from; maritime is to do with the fact that it’s coming over sea before reaching us, rather than being a continental airmass, which would mean something from Europe and over land.

“What that means is that it’s cold, because it’s coming from the polar regions. But as it comes across the sea it picks up moisture as well, hence it’s quite moist so you are getting all these showers from it rather than it just being dry cold.”

The cold snap comes after high winds brought travel chaos and power cuts to hundreds of people on Wednesday, as gusts of more than 90mph were recorded in parts of the country. A 93mph wind was recorded at High Bradfield in South Yorkshire, while Tiree was hit by a 77mph gust and South Uist by one of 73mph.

The strong winds caused damage across the country on Tuesday, with power cuts reported in Scotland and north-east England. Northern Powergrid, which supplies power to homes in the north-east and Yorkshire, said it had 545 customers without power on Wednesday morning.

The Forth Road Bridge near Edinburgh has been closed in both directions after a lorry was blown over at about 2am. No one was injured but the bridge is likely to remain closed for some time as the strong winds hamper recovery efforts. The lorry driver has been charged.