Last week the mercury in London hit 35.1°C at Kew Gardens (a new May record) and Wales recorded its hottest May day ever. Across the Irish Sea the story was the same: Shannon reached 30.6°C, a new May record set the day after the previous one was broken. Ireland’s Met Éireann was clear about the cause: high pressure, a warm air mass from the south, and a baseline that keeps climbing. Ireland’s average temperature is up roughly 1.1°C since 1900, and heat extremes are getting warmer and more frequent.
It felt like a novelty – beaches and parks full, queues for ice cream, the usual excitement of sunshine. But for anyone responsible for conditions in a global supply chain, last week was a preview, not an anomaly. The underlying trend is climate change – a steadily warming baseline that makes hot spells hotter and more frequent (among other effects). And on top of that baseline, the coming months are likely to be unusually warm for a specific reason:
A warming baseline, about to get an El Niño on top
El Niño is a recurring climate pattern – a periodic warming of the Pacific Ocean that shifts weather worldwide for months at a time. Its main effect for present purposes is simple: it nudges global temperatures up, so an El Niño year tends to run hotter than the years either side of it. Layered onto an already-rising baseline, that means more frequent and more intense heat, heavier rainfall in some regions and drought in others, and added strain on agriculture and water supplies.
The models have been converging on one forming. In mid-May, NOAA’s Climate Prediction Center moved to an El Niño Watch, putting the odds of an event emerging between May and July at 82%, rising to 96% for the December–February peak, with roughly a 65% chance it reaches strong or very strong intensity by October. Forecasters are careful as spring is a notoriously difficult time to call this (a so-called “spring predictability barrier”) but several independent models are pointing the same way, some trending toward a super El Niño, where the Pacific would run more than 2°C above average. The last of those was 2015–16, which helped make it the hottest year on record at the time. WMO’s seasonal outlook already has land temperatures running above normal across nearly the whole globe through the summer.
El Niño isn’t really a UK or Ireland story. Its sharpest effects will land first on countries bordering the Pacific, and the global temperature peak may not arrive until 2027. But here is my point: the places where your products are made, your ingredients grown, and your components assembled are disproportionately in the regions that will bear the brunt – South and Southeast Asia, the Arab states, parts of Africa and Latin America. The heatwave that had you sunbathing and barbecuing this week, for the people in your supply chain, is an occupational hazard that is very likely to intensify very soon.
So:
- Are you prepared for this?
- Are your workers protected?
- And do you actually know where this risk sits in your supply chain?
Extreme heat is a workers’ rights issue, and the numbers are already high
This is not a future problem. It is a present one. The ILO estimates that around 2.4 billion workers (roughly 70% of the global workforce) are exposed to excessive heat. It links heat exposure to nearly 19,000 deaths and around 23 million occupational injuries every year, and notes that over 26 million people are living with chronic kidney disease attributable to heat stress at work. Analysis in The Lancet put labour lost to heat exposure in 2022 at 490 billion hours, a 42% rise on the 1991–2000 baseline.
One feature of the ILO data deserves particular attention from anyone running a HRDD programme: since 2000, the fastest growth in heat-related occupational injuries has been in the Americas, followed by Europe and Central Asia – not the regions you might have first imagined. Heat is migrating into workforces, and workplaces, that were not built for it and are not equipped for it.
It is not just an outdoor problem either. The risk is often worse in indoor manufacturing — like garment factories with heat-emitting machinery, poor ventilation, and dense production floors, where ambient temperatures climb well above what’s outside.
Who is actually at risk
It is easy to picture heat stress as a field problem — someone bent over a crop under the equatorial midday sun. That image is accurate but incomplete, and the incompleteness is where supply chains get caught out. The ILO is explicit that factories, food processing plants, brick kilns, and warehouses can be as dangerous as working in the open. Below is a rough map of where the exposure tends to sit and why it often goes unmanaged.
| Where they work | Why heat builds | Why it gets missed |
| Agriculture and harvesting | Outdoor, physical, sustained exposure; the single worst-affected sector, projected to account for around 60% of working hours lost to heat by 2030 | High informality; workers paid by output keep going through the heat to earn |
| Construction and outdoor sites | Direct sun, heavy exertion, little shade; projected at roughly 19% of hours lost by 2030, and the dominant heat sector in Europe and North America | Often subcontracted and layered, so the buyer never sees the exposed worker |
| Garment and textile factories | Heat-emitting machinery, dense floors, weak ventilation; indoor temperatures climb above what’s outside | “Indoor” is assumed to mean “safe”; audits rarely measure heat on the floor |
| Food processing and manufacturing | Cooking, drying, and process heat combine with crowded production areas | Treated as a food-safety issue, not a worker-safety one |
| Warehousing and logistics | Large steel-roofed units act as heat traps; fast-paced, physical picking and loading | Peak-season order surges land in the hottest months, with no slack to slow down |
| Transport and delivery | Cabs, holds, and last-mile work with little climate control | Lone or mobile workers fall outside site-level heat plans |
| Fishing and natural resources | Sustained outdoor exertion, often remote and unregulated | Hard to monitor; frequently informal |
Across all of these, the same multipliers recur: migrant and informal workers with the least bargaining power, pregnant women, and anyone paid by output rather than time — because slowing down to stay safe means earning less. And the harm is not confined only to days that make the headlines as heatwaves: 9/10 worker heat exposures happen on ordinary working days that never trigger a warning.
Where the risk actually manifests, and where you fit in
Here is the part that tends to get skipped. Heat stress in your supply chain is not purely a function of the weather. It builds where the work is hot, hard, and under pressure – and whether you ever see it depends on whether your HRDD is set up to look.
Consider how it plays out. A peak-season order lands during the hottest months of the year. To meet it, the factory runs longer shifts, often through the afternoon, when heat indoors peaks. Slowing the line, adding rest breaks, or improving ventilation all take time and money that may be in short supply. Worker safety becomes the quiet casualty — and the real question is whether your HRDD would catch it. Most programmes are built to look for forced labour indicators, wage violations, and unsafe structures. Far fewer are calibrated to ask whether heat is building on the production floor – especially in usually temperate locations like the UK. The harm can be sitting in plain sight and still fall outside what the programme knows to look for.
None of this is a problem happening over there for suppliers to manage alone. Conditions on the floor and the commercial pressures a supplier is working within are connected, which makes heat a shared exposure with a shared interest in fixing it. The regulatory direction points the same way: the CS3D expects purchasing companies to examine their own practices that contribute to harm in their supply chain. The case for integrating your own purchasing practices into your HRDD and working collaboratively with suppliers to address the risk of extreme heat is not just moral or practical; its operational and legal too.
What being prepared actually looks like
The encouraging part is that this is one of the more tractable human rights risks, because the interventions are concrete and many already exist. The questions worth asking before the heat arrives, not during it:
- Does your due diligence know to look for heat? Map where your heat-exposed work actually is — which suppliers, which sites, which processes, in which climates — and check that your HRDD is set up to assess it, not just the risks it was originally designed to catch. A programme that never asks about heat won’t find it.
- Do your commercial terms leave room to protect people? Lead times and prices that assume nobody ever slows the line for heat leave a supplier with nowhere to go. Building that room in — and planning order timing around the hottest months — is usually a conversation worth having before peak season, not during it.
- Is there a plan at site level? Access to water, rest, ventilation or cooling, adjusted hours, and the ability to stop work safely when conditions demand it — without workers losing pay for doing so.
- Can workers raise the alarm? Freedom of association and functioning grievance mechanisms are how dangerous conditions get flagged before they become fatalities. The ILO data is blunt: where workers and their representatives can negotiate on heat, workplaces get safer.
- Are you treating this as resilience, not charity? Heat stress causes absenteeism, errors, slowdowns, and disruption. The business case and the human rights case point the same direction.
The garment sector is already moving — the International Accord has announced it will formally treat heat as a workplace safety risk and develop a dedicated heat stress protocol. That is a signal worth reading across to other sectors, not a niche development to file away.
So – Back to our 3 questions…
Last week’s records were a comfortable kind of extreme for many of us in the UK and Ireland – a heatwave you could enjoy. The version arriving in your supply chains over the coming months will not be comfortable.
So it is worth asking yourself the three questions plainly, now, while there is still time to act on the answers:
- Are you prepared for this?
- Are your workers protected?
- And do you know where this risk manifests in your supply chain?
If those three answers don’t come easily – it’s a gap worth closing before extreme heat becomes a supply chain crisis. And the CLC team can support you – mapping where the risk sits, checking your due diligence is actually built to find it, and putting something practical in place ahead of the season rather than during it.
CLC is a business and human rights advisory practice specialising in human rights due diligence, responsible sourcing and stakeholder engagement.
clairelynchconsulting.com
