The Tesco Extra in Beeston had to temporarily close on Wednesday (June 17) after floodwater poured into the superstore.
Shopper Sue Cain, 52, filmed the car park of the Station Road store partially underwater.
The charity volunteer coordinator, of Arran Close, Stapleford, also captured footage of the supermarket left damp on the inside.
She said: “It’s got to be about 4.45pm – when I arrived at Tesco there were no queues. It was raining but not tremendously, it was just a little bit.
“I came in and had a chat with the lady who was letting everybody in and went round and did my shopping.
“But then you could hear the rain starting to come down heavier because it echoes on the roof of Tesco.”
She described seeing a member of staff carrying a wet floor sign because of a leak in the store.
But it was when she made her way to the self-checkout zone when she saw the full extent of the bad weather as water came in through the door.
“From where I was stood you could actually see the door and there’s staff suddenly running around,” she said.
“Water started coming up… you could see it like a river running in the shop. It obviously had engulfed the foyer and straight towards the tills.”
Staff directed customers up an escalator to exit the store onto the upper car park.
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Those who parked in the lower car park, including Mrs Cain, were able to walk down some steps to access their cars.
“We were told ‘the only thing you can do is go across the top car park, all the way across, down the outside steps and back under’,” she said.
“My car was near the entrance – so that’s exactly what we did.”
She added: “The car was fine. There was like about three inches up the wheel (the water).”
A Tesco spokesman said: “Flooding caused by heavy rain meant we had to temporarily close our Beeston Extra store yesterday, however the store is now open again as normal and we apologise to our customers for any inconvenience caused.”
Wednesday’s torrential downpours also led to the Royal Mail centre in Padge Road, Beeston, being evacuated.
A second weather warning is in place across Nottinghamshire for Thursday (June 18) – follow our weather updates here.