Fruit and vegetables are perishing in fields and growers fear the drought and further extreme temperatures could wipe out harvests.
Suppliers are counting their losses after record temperatures last month caused crops to fail, while the hot dry weather has also led to the earliest harvests since 1976 for many farmers.
There are now fears that future heatwaves could affect food security in the UK.
Vernon Mascarenhas, of wholesaler Nature’s Choice at New Covent Garden Market in London, the largest fruit, veg and flower market in the UK, said: “It’s not just fruit, we lost entire plantings of peas, entire sowings of broad beans, baby spinach was lost, salad heads were lost.”
Last month’s record temperatures caused “major difficulties” for the berry harvest.
Mr Mascarenhas said: “The fruit is now coming back, but if there is more intense heat forecast, that would be a worry.
“At flowering season we didn’t have any frosts so were very excited, thinking we were going to have our best year ever, but the heat has killed some of it off.
“If we are going to get another impact of hot weather we could be in real trouble.”
The hotter, drier summer has led to early harvests of some crops. Farmers in East Anglia finished harvesting in July, which is “unheard of”.
Tom Bradshaw, deputy president of the National Farmers’ Union, who farms wheat, barley and oats near Colchester in Essex, said: “On our farm, we finished wheat last Thursday.
“We don’t normally start wheat until the last day of July, so it’s incredibly early and certainly unprecedented in many situations.”
He is worried about his spring barley and spring oats, which account for around 40 to 50% of his produce.
Mr Bradshaw said: “For spring-sown crops, spring barley, spring oats and peas, they were planted in March and April and the impact has been far more dramatic.
“They’ve had a lack of moisture right the way through their growing season. The yields have been hit pretty badly.”
This month’s oil seed rape planting may be delayed if the soil remains too dry, leading to a shortage of cooking oil.
Anglers fear fish will die if Southern Water is allowed to extract more water from the river Test as it deals with drought conditions in Hampshire.