Stalls in the city's market shut up shop early as trade took a hit in the extreme heat.
Temperatures reached a peak of 37C in Norfolk on Monday as the Met Office issued the first ever red weather warning for extreme heat in the UK.
Many stalls were closed by 3pm yesterday as shoppers stayed out of the scorching sun.
Some traders decided not to open at all.
Joe Metcalf, who works at the Bread Source stall, said trade was down by more than half compared to a typical Monday.
The stall would normally see more than 150 sales but it was at 70 by the time the shutters were being put up around 3.30pm.
Mr Metcalf said: "We are always quiet but today has been particularly quiet. A lot of the others have shut around me.
"It's been very hot on the market. I went out to buy lots of water and there is a fan here.
"But I would not say the heat is unbearable. People are shutting because there is no one around rather than being too hot."
But for others, sales went surprisingly well despite limited footfall in the city centre.
The Churros for the People stall saw a surge of customers around lunchtime.
Owner Hugo Malik said: "I was tempted not to open but if I make the effort when it snows in the winter, it is worth staying open for the people who want to eat when it is hot.
"I think people knew it would get incrementally hotter as the day went on."
Mike, Debs and Sons Fruit and Veg saw cucumber and salad sales go well for those enjoying a barbecue or glass of Pimm's in the heat.
Business owner Mike Read said: "It was busy this morning then died off after lunch from around 2.30pm. It is very quiet.
"We can't put as much produce out because it could spoil it. It is a case of buying a lot less and selling a lot less but it is only two days of the year.
"Most people are sensible enough to realise to keep in the shade."
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