"Extensive damage" was done to carpets and flooring at some businesses in Thetford as heavy downpours caused widespread flooding.
Norfolk Fire and Rescue crews attended 20 callouts as the town was battered by the rain.
The A134 – the main road between Thetford and Bury St Edmunds – was completely covered in flood water, as was Bridge Street in the town centre.
The clean-up operation was in full swing on Wednesday morning to clear sewage and dry out places where the flood waters had got inside.
One such place is the Charles Burrell Centre, a community and business centre based in Staniforth Road.
Its chief executive Nik Chapman said the water had done some damage to the interior of the building, affecting some of the businesses which trade there.
He said: "The Charles Burrell Centre suffered flooding from the downpour yesterday evening.
"It was sheer intensity and volume of water in a short space of time – the drains could not cope and water level rose by eight inches in some places to flood into the building.
"Luckily no mix of sewage but extensive damage to carpets and flooring in public spaces and individual businesses."
The centre advised customers that it would be closed on Wednesday, though Mr Chapman said it would try to reopen gradually throughout the day as areas are cleaned up.
He praised the response of staff and their families, who all came out on Tuesday evening to start the clean-up.
Mr Chapman said: "Great response from the Charles Burrell Centre team, and co-opted family members, to start the clean-up last night.
"Also, a great response from tenants with everyone supporting each other. That is the community spirit.
"Like others in the town who were flooded, with fortitude and a can-do attitude we will bounce back.
"As someone said, what is the next challenge to be thrown at our feet? Hopefully not a plague of locusts."
The Charles Burrell Centre is home to more than 50 organisations and also hires out rooms for meetings and events.
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