The Sauchiehall Street branch in Glasgow was evacuated as videos showed torrential rain causing the ceiling to collapse on Monday. Footage on social media showed a deluge of water lash through from the store's roof into the aisles. The floodwater was seen rising on the shop floor while stock floated.
Customer Joanna McDonough, who filmed the incident, said she was "quite scared" by the flooding.
But she also praised staff for their "speedy evacuation" of customers inside.
She wrote on Twitter: "There was a huge bang first then the water burst in - I thought we were going to be trapped.
"Well done TK Maxx Glasgow for the speedy evacuation of the customers following torrential rain and a ceiling collapse. Quite scary."
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But he added the movement of the rain meant they were not over any one spot for that amount of time.
He added: "When you've got these large, potentially thundery, heavy showers moving through, when you're under the core of the rainfall, it's very intense and the rain's coming down at a high rate."
Flooding also caused havoc in other regions of Scotland this week.
Other social media footage showed vehicles getting stuck while travelling through water in Drumchapel, near the city.
And one car was even seen sinking under a bridge.
Elsewhere, a number of streets in Glasgow, including in the Pollokshields area, were left flooded due to the rain.
ScotRail also imposed speed restrictions on a number of its routes earlier in the week.
A section of the A8 dual carriageway was entirely flooded, which lead to heavy traffic.