With UK temperatures exceeding 30°C several times in recent months, Dr Stuart Kings, NEC4 drafter and technical director at construction contract management software provider Sypro, explains how increasingly severe heat could leave contractors carrying greater risk, and what project teams can do to protect programmes, costs and margins.
Recent research from the University of Reading found that more than half of construction leaders have seen heat increase project costs, while almost as many have experienced delays. Yet fewer than four in 10 organisations have a budget for weather adaptation, leaving many project teams exposed as temperatures rise.
For contractors, extreme heat is no longer just a health and safety challenge. It is becoming a commercial and contractual risk that can affect productivity, programme certainty and ultimately project profitability.
The central challenge for UK construction is unpredictability. Civil engineering projects and other outdoor works cannot simply avoid severe weather, while exposed activities such as bricklaying and glazing are particularly vulnerable. Heat can reduce productivity, disrupt sequencing and make physical work impractical for extended periods, increasing pressure on programmes, site resources and margins.
Construction contracts have long included mechanisms for dealing with extreme weather, although some provide greater clarity than others. NEC takes an objective approach, while JCT refers to ‘exceptionally adverse weather conditions’, which can leave more room for interpretation.
Under NEC4 Engineering and Construction Contract clause 60.1(13), a weather measurement must occur less frequently than once in 10 years to qualify as a compensation event. This means contractors should not assume delays caused by high temperatures will automatically result in additional time or money.
However, as severe conditions become more frequent, they could increasingly form part of the expected baseline. Today’s exceptional heat may become tomorrow’s standard construction risk, leaving contractors responsible for more disruption when the contractual threshold is not met.
That makes proactive planning more important than ever. Contractors should be considering the impact of hotter summers when pricing work, preparing programmes, discussing risk allocation with clients and identifying activities most vulnerable to extreme heat before work even starts.
Only genuinely exceptional conditions are likely to qualify for compensation, so contractors must consider higher temperatures when planning programmes. This could mean scheduling exposed activities at different times of year, adjusting working patterns during hotter periods or identifying alternative tasks that can continue indoors.
The early warning process is an important tool in managing this risk. Anything that could increase costs, delay completion or impair the performance of the works should be raised as soon as it becomes apparent.
An early warning does not automatically create an entitlement to additional time or money. Instead, it allows the project team to act before the impact escalates. For example, a client may be able to release internal areas of a building so work can continue while external activities are disrupted.
Clients and contractors should consider expected conditions when preparing programmes, allocating risk and deciding when exposed work will take place. They should also retain clear weather records, programme updates and evidence of any impact on productivity, time or cost.
Digital contract management can strengthen this process by bringing communications, early warnings and compensation events into a single source of truth. Robust audit trails and timely assessments provide clarity over responsibilities, helping project teams respond collectively, minimise disruption and protect already tight margins.
Contractors cannot control the weather, but they can control how well they prepare for it. As periods of extreme heat become more common, those that treat weather as a foreseeable project risk, rather than an exceptional event, will be better placed to protect programmes, costs and margins, while reducing the likelihood of costly disputes.
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