Frost is due to set in overnight as temperatures across the UK plummet.
That means a 13.6-degree drop from last week, when the mercury nudged 23.6C in Kew, west London, and Gravesend in Kent.
Daytime temperatures on Wednesday were expected to hit a maximum of 10C, predicted to fall to 2 or 3C overnight.
The average overnight temperature for November is around 3.3C.
The North and Scotland will experience the coldest weather, with rural areas in northern Scotland expected to drop to -5C.
However, this falls short of the coldest ever Bonfire Night in 1968, when a temperature of -11.1C was recorded in Braemar, Aberdeenshire.
Maximum temperatures in northern England will be 1 or 2C overnight.
City-dwellers are expected to escape the coldest conditions, and the lowest temperatures will set in in the early hours of the morning, so people going out to watch fireworks this evening are more likely to experience temperatures of 5 or 6C.
Laura Young, a spokesperson for the Met Office, said: "Temperatures will be colder than what you would expect it to be for the beginning of November.
"Most places will see a bit of frost around tomorrow morning - it's likely that you're going to have to scrape your car.
"Today it's going to be a warm, sunny day, so not a bad 5th of November."
However, the clear, dry weather won't stay for long, as heavy rain is predicted for the rest of the week.
Around 25mm of rain is predicted to fall in south-west England and in west and central Scotland and Northern Ireland, which could cause surface water flooding.
The unseasonably warm weather has also caused trees to stay in leaf, which can exacerbate flooding as strong winds blow leaves off trees and block drains.