Sub-zero temperatures will reach some parts of the UK by the end of this week, bringing to an end a stretch of mild autumn weather.

Temperatures look likely to fall below zero in some parts of the country by Friday, with forecasters saying a cold blast will make parts of the UK feel like they have been plunged into an early winter.

Parts of the UK enjoyed warm weather and blue skies during the weekend – with temperatures hitting 20C (68F) in parts of the south-east. However, by the end of the week, some areas in Scotland and northern England can expect snow showers and gale-force winds.

Strong winds will batter parts of northern England and Scotland, reaching 50mph in exposed and coastal regions. Northern Scotland, especially Orkney and Shetland, are likely to be the worst hit. Temperatures will be low enough for wintry showers in northern England, particularly across the Lake District and the Pennines. There is also a risk of high tides in the north-east of the country.

This week, however, much of the country will see blue skies and temperatures in the mid-teens until Thursday, with a cold snap sweeping in by the start of the weekend, said Luke Miall, forecaster at the Met Office.

“It’s the first cold snap of the season and it will feel like a bit of a shock,” he said. By Tuesday, the north of Scotland will become wet and windy, while southern areas will be mostly dry with spells of sunshine and fine weather, with temperatures reaching up to 17C to 18C on Wednesday.

Miall said: “But as we go into Thursday, most places will start to see the change in weather and, while much of England and Wales start off fine, rain will start to push down from Scotland, bringing colder air behind it. By Friday we see that colder air hitting the whole country, with highs of 7C to 8C in the north and 9C to 10C in the south. There will also be strong winds, with a biting edge especially on the northern coast.

“It’s not completely unusual to see this weather at the end of October, but because we’ve had a warm autumn so far – which followed a dry, hot summer – it will feel like a bit of a shock to the system.”