Recent weeks might have suggested an early summer , but Britain is now in for a reality check as ice , rain and snow arrive with -5C ( 23F ) temperatures . The colder weather is set to last the first half of May - and the forecast comes less than a fortnight after the mercury breached the 25C ( 77F ) mark . Conditions this week are set to be average for April , with showers on the way and temperatures barely in double figures for most of the country . Sleet and snow are forecast for today and tomorrow from the Pennines northwards , and there were small accumulations yesterday in the Cairngorms . Meanwhile the Met Office has a severe yellow ‘ be aware ’ ice warning for north-east Scotland , warning motorists of a disruption risk until 7am today . Scroll down for video . Getting colder : Visitors to Alnwick Garden in Northumberland enjoy the weather yesterday , with conditions expected to turn this week . Going for a walk : Visitors to Alnwick Garden admire the spectacular blossom on Prunus serrulata 'Taihaku ' trees in the Cherry Orchard . Polar plunge : This graphic from Netweather shows the temperature at 850hPa ( 5,000ft ) and the pressure at sea level as of midnight today . Forecast : Conditions this week are set to be average for April , with showers and temperatures barely in double figures for most of the UK . It comes after Britain enjoyed what appeared to be one of the warmest Aprils on record , with a 2014 high of 25.1C ( 77.2F ) recorded in Kent on April 15 . And Pershore in Worcestershire had the UK 's top temperature of 14.8C ( 58.6F ) yesterday , while Morecambe saw 14.1 hours of sunshine . But the dramatic change is being brought in by a ‘ polar plume ’ - a cold mass of air moving down from polar regions . Met Office meteorologist Charlie Powell told MailOnline last night : ‘ It will feel cooler - temperatures are going to be around average . ‘ But because we have been used to things being so warm in recent weeks , we are going to notice the change. ’ More than 38,000 marathon runners in London yesterday were caught on the brink of the cold front , as cloudy , damp weather greeted them at the start . Surface pressure : A cold front ( in blue triangles ) can be seen moving away from Britain at midnight today after arriving over the weekend . Cloudy , damp weather at the start : More than 38,000 marathon runners in London yesterday were caught on the brink of the cold front . Better weather : Lily , 11 , and Jack Manning , six , enjoy the sunny weather in Portsmouth , Hampshire , only six days ago on Monday , April 20 . Warmer days : People enjoy the warm weather at Jubilee Gardens next to the London Eye in the centre of the capital on Saturday , April 18 . The mercury is expected to fall as low as -2C ( 28F ) early this morning in built-up areas , while rural parts could see -5C ( 23F ) , this week ’ s expected low . This morning will see a frost , Mr Powell said , and showers are expected to arrive from the west today , with eastern parts forecast to be the driest . And today Britain is even expected to be colder than the Norwegian capital Oslo , which will reach around 13C ( 55F ) . Temperatures will be around 12C ( 54F ) for most , although the far South East could see up to 15C ( 59F ) - but that will come with a few showers late on . Tomorrow and Wednesday will also be showery days , with overnight temperatures around freezing and highs of 14C ( 57F ) in the daytime . A similar high could be seen on Thursday and Friday , but there is expected to be more sunshine , fewer showers and lighter winds by this point . Conditions will marginally improve for the beginning of the Bank Holiday , with dry and mild weather predicted for the Friday and Saturday . Early forecasts for the Bank Holiday weekend suggest the North East will see the best weather into Saturday - but could still be hit by showers . How it works : This Met Office moving graphic shows how the arrival of an Arctic Maritime air mass is affecting temperatures in the UK . A pair of dolphins arrived on the south coast of England yesterday , with hundreds of residents enjoying the spectacle . The common dolphins , normally found offshore in deep waters , spent several hours swimming around Weymouth Harbour in Dorset . And 48-year-old resident Madeleine Santonna told the BBC : ' I 've lived by the harbour all my life and I 've never seen anything like it. ' . Spotted at the harbour : Two dolphins swam around Weymouth in Dorset for several hours yesterday , causing excitement among onlookers . Unusual appearance : The common dolphins seen at Weymouth Harbour yesterday are normally found offshore in deep waters in large groups . Unprecedented sighting : One local resident said she had lived by the harbour for her whole life - but had 'never seen anything like it '
Colder weather set to last this week and into first half of May - less than a fortnight after storms hit 25C . Snow from Pennines northwards today , while much of town will see showers and Scotland has ice warning . Maximum temperatures this week of around 15C in far South East , with -5C expected in rural areas overnight . Early Met Office forecast for Bank Holiday weekend in North East will bring best weather into 2020 .