The big chill gripping the UK will guarantee an uncharacteristically freezing Easter weekend and could last until the end of April, weather forecasters have warned.

Temperatures are unlikely to recover to normal averages for the time of year until late next month, the Met Office said in its regular 30-day forecast.

Sub-zero temperatures are expected to bring misery to thousands for the rest of the week and throughout Easter weekend as conditions show no sign of abating.

The Met Office issued a cold weather alert for much of England, with a 100% probability of severe cold weather and ice until Friday. Its outlook for Sunday until Tuesday 9 April predicts cold, dry weather, with a few light snow flurries and widespread frost and icy patches overnight. And it warned that temperatures are unlikely to recover to closer to normal levels until the latter part of April.

Ladbrokes now has a white Easter as odds-on and is offering 5/1 that it will be the coldest Easter weekend ever. William Hill is offering 25/1 that Sunday's Oxford-Cambridge University Boat Race – last year sabotaged by a swimming protester – will experience snow.

In western Scotland thousands endured a sixth day without power after being cut off last week, and across the UK many transport routes remained impassable because of deep snowdrifts.

After embattled sheep farmers reported the deaths of thousands of lambs in snow-affected areas such as Shropshire, north Wales, west Cumbria and the Peak District, the supermarket Waitrose said that from Thursdayit would be delivering 30,000 "macs" (light plastic coats which are 100% biodegradable and recyclable) to protect lambs against harsh weather conditions to farmers it works with in Wales and the west country. Retailers said supplies of lamb had not been disrupted before the Easter sales peak, but the National Farmers Union warned that there could be disruption later. Sales of lamb were down 30% this week compared with the week before as farmers struggled to get to market.

In the east of England high winds have caused snowdrifts while in the south-west freezing temperatures and waterlogged conditions have combined to cause flooding and a washout for campers and campsite owners. At Arthur's Field, a 63-pitch campsite in Treloan, Cornwall, only 25 families had booked for the bank holiday weekend, but half of those had already cancelled.

Jon Dale, spokesman for the UK's Camping and Caravanning Club, said: "The adverse weather conditions during March have had an impact on our Easter bookings. However, we're still reassured by the number of people still wanting to pitch up with us."

The cold snap has triggered some unforeseen retail trends. With popular spring flowers blooming late this year, John Lewis is stocking fake daffodils for the first time and is reporting a year-on-year 18% increase in sales of fake flowers overall. It has also started selling artificial bluebells – another early spring flower being curtailed by the dreary weather.

Marks & Spencer said sales of mulled wine were up by 50% over the past week. The retailer normally stops stocking the winter favourite by the end of February.