When temperatures rise: can heatwaves constitute force majeure under English law?
29th June, 2026
2026 has seen unprecedented June temperatures in the UK, with red weather warnings, transport disruption and temperatures approaching 40°c, although not quite hitting these heights in our Newcastle office.
High temperatures in summer months are no longer isolated events, and are increasingly a recurring operational risk for businesses.
In considering that operational risk, can a business build in any protection to its contracts with customers or suppliers? Can extreme heat excuse performance?
As with many force majeure issues under English law, the answer is highly fact and wording dependent.
Why heatwaves are becoming a contractual issue
Extreme heat can impact performance in a number of ways, including:
- transport disruption (e.g. rail cancellations or restrictions, road deterioration)
- cancellation of events
- workforce constraints and health & safety limitations
- reduced productivity or site shutdowns
- supply chain delays
Force majeure clauses are typically seen as boilerplate provisions in commercial contracts, something to drop into the back of the contract, but with very little thought given to specific risks which could impact performance. However, force majeure was brought into the spotlight during recent times, including during the Covid pandemic.
Heatwaves have not historically been front of mind in force majeure drafting. That is now changing as suppliers begin to consider mitigation of operational risk.
Force majeure under English law, a reminder
There is no general doctrine of force majeure under English law. Relief depends entirely on the specific wording of the contract.
Typically, a force majeure clause will:
- define certain events or categories of events as force majeure
- provide contractual relief where that event prevents, hinders or delays performance.
Are heatwaves covered by standard clauses?
If the clause refers to extreme weather, adverse climatic conditions or acts of God then a sufficiently severe heatwave is capable of falling within scope.
However, the position will turn on the exact wording of the clause, and of particular relevance is whether the contracting party could reasonably control the circumstances, and whether the events were foreseeable.
As heatwaves are increasingly foreseeable, this will likely make reliance on force majeure more difficult in future.
Prevention vs disruption
A key distinction is between disruption and prevention. Only events which actually prevent performance are likely to trigger force majeure.
Crucially, force majeure clauses do not interfere to re-write a contract where the contract simply becomes more difficult to perform due to a heatwave (for example where the supplier would operate at a loss or miss service levels and incur service credits).
Mitigation
Parties are typically required to take reasonable steps to mitigate impacts, such as adjusting working hours or sourcing alternatives.
Health and safety and employment
What if you are a service provider with staff working in extreme heat?
Employers must ensure health and safety of workers and provide a reasonable working temperature. There is no maximum temperature in UK law, but risks must be assessed and managed.
Where conditions become unsafe, this can support a force majeure argument where the event is covered by the clause, and where that prevents performance.
However, discomfort or reduced productivity will not usually be enough. Suppliers must still mitigate, for example by changing working patterns or implementing cooling measures.
This creates a tension between contractual obligations, employer duties and health and safety duties, often requiring pragmatic engagement with customers and staff.
Practical steps
Businesses that are in an industry where they are particularly prone to the impact of heatwaves (for example events and hospitality) should consider how they would deal with cancellation or inability to perform, and include express terms in their contracts with clients.
Relying on general boilerplate force majeure clauses is unlikely to give the required protection, much like failing to apply the factor 50.
If you would like to discuss how force majeure provisions apply to your contracts or would like support reviewing or drafting clauses to address weather-related risks and other unforeseen events, our Commercial team would be happy to help. Please get in touch Matthew Cormack to discuss your circumstances and ensure your contracts are fit for an increasingly unpredictable operating environment.
Please note that this briefing is designed to be informative, not advisory and represents our understanding of English law and practice as at the date indicated. We would always recommend that you should seek specific guidance on any particular legal issue.
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