Bottled water is running low in some shops, as industry chiefs issued a fresh warning of wider shortages.
The heat wave is believed to have fuelled a spike in demand for mineral water.
On Tesco’s website, several mineral water multipacks were showing as unavailable.
And in a branch of Sainsbury’s visited by the Mirror on Tuesday evening, the section for water was almost stripped bare, with signs saying: “Please bear with us. We’re experiencing high demand.”
The jump in water sales is expected as temperatures soar.
An industry insider said: “It makes sense that sales have gone through the roof in the last few days.”
The Mirror has seen empty bottled water shelves in Tesco in Pinner
Sainsbury’s said any disruption to supplies was likely to be “store-specific.”
However, it comes amid claims of bottled water shortages in recent weeks.
The heat wave has also led to reports on social media of ice cream shortages.
A Tesco spokesperson insisted: “We have good availability of ice cream across our stores.
“We’ve seen huge customer demand for ice cream and lollies during the recent warm weather, but our colleagues are working hard to make sure our freezers are kept fully stocked.”
More empty water bottle shelves in Tesco
It follows recent reports of a hit to supplies of other products.
The wider situation, which has been seen over several months, has been caused by a “perfect storm” of factors, from the Covid crisis to the fall-out from Brexit.
Trade body the Builders Merchants Federation said worker and product shortages were having a “significant impact on the construction industry’s supply chain across the UK.”
BMF chief executive John Newcomb said: “The supply chain is stretched, but our members are pulling out the stops to keep supplies in branches and deliveries out to customers in very demanding circumstances.”
It came amid warnings that the supply chain to manufacturers was “teetering on the edge of collapse” this summer”, needing urgent Government intervention.
Enginuity, a not-for-profit engineering skills body, blamed among other factors a Brexit exodus of European drivers, Covid testing delays at UK and European ports and self-isolation.
Ann Watson, chief executive of Enginuity Group, said: “This constitutes a very dangerous situation which threatens to derail the Covid recovery.
“We are on the verge of a crisis which threatens the viability of manufacturing across the country – we need some urgent intervention from Government.”