A third of consumers (31%) plan to do their main Christmas food shop today, according to a poll of 2,200 people for BBC Good Food.
Waitrose predicts the hour from 11am will be its busiest period, with sales expected to be 3.5 times higher than on a typical Wednesday, while the busiest branch is expected to be Oakgrove in Milton Keynes.
Sainsbury's expects its checkouts to hit their peak between 11am and 1pm and Tesco has taken on extra staff to prepare for what it predicts will be its busiest in-store shopping day.
Visa Europe predicts that high street spending on its cards will reach £1.3bn, peaking between 1pm and 2pm when 3.2 million transactions will take place, making it the biggest shopping day of the year.
Shoppers are expected to make more than 37 million transactions, up 10% on last year, while the overall amount spent is predicted to be 3% higher.
Kevin Jenkins, Visa Europe managing director for UK and Ireland, said: "Brits will race to the high-street to pick up last-minute presents, despite starting their Christmas shopping early this year with record amounts spent online on Black Friday.
"In keeping with previous years, the busiest day for Christmas shopping this year will be two days before Christmas where we are likely to see £1.3bn spent on the high street.
"More than £1m will be spent on Visa cards every minute, rising to nearer £2m every minute during the lunch time rush between 1pm and 2pm.
"Shoppers will demand quick and easy purchases during this busy period, and retailers with a contactless offering are likely to be the winners as they could see shorter queuing times and happier customers."