Portugal sizzled through its hottest May day ever recorded this week, with temperatures in the Algarve hitting 36.9°C. The mercury has not climbed that high in the month of May since records began.
For the UK, still shivering through a damp spring, the news is a red flag. Weather models used by the Met Office are now projecting a 60 per cent chance that southern England will see temperatures above 34°C before the end of June. For millions of workers in warehouses, kitchens, and construction sites, this is not a forecast of lazy summer afternoons.
It is a warning that the real economy is about to become unbearably hot. The Trades Union Congress has already called for an immediate review of workplace heat regulations. Current rules only advise that temperatures should be 'reasonable' and do not set a legal maximum.
Union leaders argue that a 30°C threshold must be introduced for indoor work, with compulsory breaks and access to cool drinking water. 'No worker should be expected to toil in conditions that could kill them,' said Frances O'Grady, the TUC general secretary. 'We saw last year what happens when the government doesn't act.
People collapsed on the job, and productivity plummeted.' The warning is particularly acute for the 1.2 million people employed in warehousing and logistics.
Many of these jobs are paid at or near the minimum wage, and workers cannot afford to turn down shifts even when temperatures hit dangerous levels. In the summer of 2022, a Royal Mail depot in Berkshire recorded internal temperatures of 38°C. Staff were found to be taking salt tablets to stay on their feet.
The cost of living crisis adds another layer of pressure. With food prices still rising at 13 per cent, families cannot afford a lost day's pay. Yet working in extreme heat can trigger heatstroke, kidney damage, and heart attacks.
The Health and Safety Executive recorded 19 work-related deaths from heat exposure between 2016 and 2021. That number is expected to rise. The government's heatwave plan, updated in March, focuses on public health messaging and checking on elderly neighbours.
There is no mention of workplace protections. 'It's like telling people to stay inside while their kitchen is on fire,' said a Unite union organiser in Manchester. 'They still have to go to work to feed their kids.
' The Portugal record is part of a broader pattern. May temperatures across western Europe have been 2°C to 4°C above the 1991-2020 average. The jet stream is weakening, and high pressure systems are hanging over the continent for longer.
For Britain, this means not just hot days but humid nights that prevent recovery. The Met Office has warned that the heatwave expected in late June could last up to 12 days. That is the same duration as the 1976 summer drought, but this time with higher base temperatures.
The economic impact will be severe. A study by the London School of Economics last year estimated that extreme heat reduces UK labour productivity by 1.2 per cent per degree over 28°C.
In construction, the hit is far worse: 2.5 per cent per degree. For retail and hospitality, footfall drops as customers stay home.
Small businesses, still recovering from the pandemic and energy price shock, cannot afford another summer of lost trade. 'We've had three days of sun and people think it's heaven,' said Rita Paulo, a bakery owner in Leeds. 'I worry about my staff.
The ovens are on all day. It's going to be a long, hot fight.' The Portugal record should be a wake-up call.
But with no legal temperature limit and no mandatory cool-down zones, the burden falls on workers themselves to demand better conditions. Unions are planning 'heat action' days in June, where members will walk out if temperatures exceed 30°C. The next few weeks will test whether the government is willing to step in or leave workers to sweat.
