Above 25.1C, people stop going shopping. Above 24.2C, they become less willing to travel to work.
Those two figures come from Barclays research reported on 27 August, and they are unusual in that they put a specific threshold on something normally discussed as a season.
A single decimal place is a strong claim from card and behavioural data, and it should be read as the centre of a range rather than a switch. But the finding underneath it is robust enough to plan around: warm weather helps trade and hot weather stops it, and the crossover is somewhere in the mid-twenties.
Two Degrees Apart, Two Different Problems
The commuting threshold sits below the shopping one, and the gap is the interesting part.
People give up the journey to work before they give up the trip to the shops. That ordering makes sense once you consider what each involves: commuting means a crowded train or a car in traffic at a fixed hour, usually twice, with no option to wait for the cooler part of the day. Shopping can be moved to the evening, or done online.
For an employer the practical consequence is that heat reaches the workforce roughly a degree before it reaches the customer. Staffing problems arrive first, and the revenue effect follows.
It also means the two effects can hit the same business on the same day in the wrong order: a retailer short of staff in the morning and short of customers by the afternoon.
A Quarter of Small Businesses Lost Productivity
More than one in four small businesses reported that hot weather negatively affected productivity.
That is a striking share for something most firms do not budget for. Cold is planned around, because heating is a line item everyone has and winter disruption is expected. Heat has historically been treated in Britain as a pleasant anomaly rather than an operating condition.
Small firms are the most exposed, and not because they care less. They are likelier to occupy older buildings they do not own, likelier to lack the capital for a cooling retrofit, and much likelier to have no slack when someone cannot work. A firm of eight people loses an eighth of its capacity when one person goes home.
They are also least able to offer the flexible response that larger employers use, because a shop or a workshop has to be open when it says it is open.
What 60% Are Actually Doing
The headline figure is that 60% of businesses are investing in, or considering investment in, technologies to adapt to extreme heat.
The phrase “or considering” is doing real work there, and the honest reading is that intent is running well ahead of installation. A survey that separates the two would tell a very different story, and this one does not.
The listed responses split neatly into two kinds. Additional employee breaks, flexible working and altered hours cost almost nothing and can be introduced tomorrow. Cooling systems cost capital and take months.
Most firms will do the first three and describe the fourth as under consideration, which is exactly what the survey wording captures. That is not evasion, it is sequencing, but it does mean the 60% should not be read as 60% of buildings getting cooler.
Cooling Runs on Expensive Electricity
There is an awkward interaction between this advice and another figure published the same day.
Civitas reported that UK manufacturers paid an average of £238 per megawatt-hour for electricity, roughly four times what some international competitors paid, with total manufacturer energy spending of about £16.6 billion in 2024. At US prices, the report suggests, that bill could have been around £5.2 billion lower.
Cooling is electricity. Telling British firms to install air conditioning is telling them to add load to the most expensive power in the comparison, and to add it precisely when everyone else is adding load too, which is when wholesale prices peak.
The same constraint runs through the rest of the industrial picture, where power costs can exceed a producer’s entire value added. Adaptation is not free anywhere, but it is more expensive here than in most of the economies Britain competes with, and the gap widens on exactly the days the cooling is needed.
That argues for the cheap measures first, and for passive fixes such as shading, ventilation and insulation ahead of mechanical cooling, on cost grounds rather than environmental ones.
Someone Is Already Selling the Answer
One number in the research is a straightforward commercial signal. Barclays corporate clients specialising in air conditioning saw cash inflows rise 4.3% year on year in the second quarter.
That is measured money moving, not stated intent, and it is the most reliable line in the release for that reason. Survey answers about future investment are cheap; a supplier’s receipts are not.
A 4.3% rise is solid rather than spectacular, which fits the picture of a market where consideration outpaces installation. If the 60% converted, that figure would be considerably larger.
For anyone in the trades, the read is that demand is real and early. For everyone else, it is a reminder that adaptation spending is somebody’s revenue, and the firms positioned to capture it are already visible in the banking data.
Warm Helped, Hot Hurts
The finding that matters most for a retailer is that weather is not a single variable with a single sign.
Earlier this summer warm weather and promotions lifted retail sales by 1% in June. Now the same category of factor is being reported as a drag. Both are true, and the threshold is what reconciles them.
Below the line, warmth pulls people out of the house and into shops, pubs and garden centres. Above it, the same weather keeps them at home or online. A summer that produces more days on the wrong side of 25.1C is therefore not simply a better version of a mild one.
The travel figures in the same release hint at where displaced spending goes, though they should be read carefully because holidays are booked months ahead and cannot respond to a given week’s weather. Overall travel spending was down 0.3% year on year in July. Airline spending fell 6%, while hotels, resorts and accommodation rose 2.6% and travel agents rose 2.5%.
A six-point gap between flying and staying is a large divergence inside a category that barely moved in aggregate. Whatever is driving it, the headline figure conceals a substantial change in what people are buying, and a business reading only that number would conclude nothing had happened.
That is the same lesson the temperature thresholds teach. A single figure for weather, or for travel, or for retail, averages together behaviours moving in opposite directions, and the average is the least useful part of it.
The planning implication is that weather forecasting becomes a demand-planning input rather than an excuse offered afterwards. Thresholds are also more actionable than trends. A firm cannot do much with the statement that summers are getting warmer, but it can do a great deal with a specific number attached to its own trading pattern, because that number turns into a rule: above this forecast temperature, change the rota, move the delivery, adjust the stock. A retailer who knows the threshold can staff, stock and schedule deliveries around it, and can stop treating a hot week as an unforeseeable event when it is now a recurring and increasingly predictable one.
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