Of all the measures you might take to see how this summer’s climate change-powered heatwaves are wrecking the UK, the price of a cucumber is one of the less obvious. But it is one of the most revealing.

The wholesale price of cucumbers has more than doubled since the first UK heatwave struck in May, according to new government figures. And savoy cabbages have jumped by 14 per cent, in what farmers are calling a “disastrous summer for British brassicas”.

“Fields of broccoli, cauliflower and cabbage have now stopped growing and have become dormant,” the Brassica Growers Association has reported – one of many dire warnings of late from UK farmers working across fruit, vegetables, cereals and livestock, as The i Paper has reported.

After the driest July on record in England and Wales – and with 45 million people now living in drought conditions in the UK – they are expected to see their worst harvest on record this summer.

And the picture is the same across Europe, with temperatures reaching over 40°C in key crop growing areas like Spain and France, meaning there is no plentiful alternative supply of fruit and veg for British shoppers. European farmers are warning of poor harvests and rising prices of everything from lettuce and olive oil to carrots and leeks.

Farmers in South Korea, meanwhile, are reporting that potatoes are “boiling” in the hard, parched, heated ground before they could be harvested. “It’s not just one or two fields like this,” a farmer told the Japanese news agency SBS. “How can I even put it into words? It’s so upsetting.”

So, your shopping basket will get more expensive. But how much more expensive? Most of the burden will fall on retailers. The price rises we will see in the shops in the coming weeks and months as these poor harvests feed through to the shelves will not be anything like as big as the increase in the wholesale price. This is the price at which retailers buy produce from farmers, and it includes significant costs for packaging, transport, storage and labour. But price rises at the shops will still be significant.

A study by the University of East Anglia indicates that a 10 per cent rise in wholesale fruit and vegetable prices could translate into an increase of around 1 to 2 per cent at the checkout, depending on the crop and the time period. This implies that somewhere in the region of 10 to 20 per cent of the rise in the wholesale price is typically passed on to the consumer.

Data on wholesale prices is patchy with government figures only covering a fairly small selection of “barometer” foods. But these do give a good early indication of how things will change as summers get hotter and hotter.

“The wholesale price rises we are seeing for some fruit and vegetables are an early warning of the pressure extreme heat can place on the UK’s food system,” Chris Jaccarini, a food analyst at Energy & Climate Intelligence Unit, told me.

And, to make matters worse, these increases come after a prolonged period of food price rises due to high energy costs and a succession of poor harvests. These have pushed the overall cost of food in the supermarket up by about 40 per cent since July 2021, just before the never-ending cost of living crisis began to gather momentum. And experts say that, the way things are going, we could well see that increase to 50 per cent in the next year or so.

And shoppers face a shortage of cucumbers as well as price hikes, after extreme heat hit production of a vegetable that Britain usually imports from Spain and Morocco. As such, the wholesale price of cucumbers in the UK increased from a cost of £1.24 per kg in late May, before the first heatwave of the year, to £2.09 per kg now – a rise of 85p, or 69 per cent.

The UK is largely reliant on overseas suppliers, importing about 80 per cent of the cucumbers it eats, with only a fifth produced by domestic farmers. As a result, experts expect supplies to remain tight for weeks.

Cucumbers aren’t the only produce going up. Tomatoes could be next, with anecdotal reports suggesting wholesale prices have already jumped by about 60 per cent in the UK over the summer.

In southern France, the tomato industry is reporting a 50 per cent decline in production due to the heat. By contrast, the amount of sunshine here has given Britain a bumper tomato crop but, as with cucumbers, the UK only produces about a fifth of its supply.

Livestock are also suffering from the heat, at a significant cost to both their health, fertility and production, which, in the case of dairy cows, can fall by as much as a fifth when it gets really humid. Across the May and June heatwaves, 25 million fewer pints of milk were delivered from UK farms, according to ECIU.

As Ruth Grice, a dairy farmer from Leicestershire, put it: “The cows were hot and bothered and were obviously prioritising staying cool over producing milk. When we did the night checks they were standing around the water troughs for relief from the heat, whereas normally they would be quietly sleeping or ruminating.”

So what can UK households do to keep their food bills down? Unfortunately. there are not really any “heatproof” foods as such in the short term – although in the longer term, British farmers may look to switch to crops more suitable for the changing climate, such as olives and grapes.

But for now, there are a handful of items that might be worth a look if you want to try and keep a lid on your shopping bill, according to Jaccarini. These include blackberries – which “have ripened early, but prices look stable” – while bell peppers have actually come down slightly since late May.

Finally, apple prices are also quite stable – with apples at this time of the year either coming from southern hemisphere producers such as South Africa and New Zealand or being domestically produced apples that have been put in cold storage, he says. It would seem that a blackberry and apple crumble beckons.