Weather Delays — Exceptionally Adverse Conditions

Weather is the original force majeure of construction projects. Every contractor prices for weather risk, every programme includes weather allowances, and every project is delayed at some point by conditions beyond the contractor’s control. But the contractual entitlement arising from weather delays is strictly defined — and significantly more limited than many contractors assume.

The Problem

The common misconception is that any weather delay generates an entitlement to an extension of time. In fact, most standard forms limit the EOT entitlement to weather conditions that are ‘exceptionally adverse’ — a threshold that requires comparison with historical meteorological records for the site location. Ordinary bad weather — rainfall at twice the monthly average, a cold snap that is unpleasant but not exceptional — does not qualify. The contractor priced for weather risk and is expected to bear it.

The second common misconception is that an EOT for weather also generates a cost entitlement. Under JCT and most FIDIC forms, it does not. The contractor gets time but not money.

The Legal Principle

Under JCT SBC 2016, Clause 2.26.9 lists as a Relevant Event ‘exceptionally adverse weather conditions’. The phrase ‘exceptionally adverse’ is not defined in the contract, but is understood by reference to meteorological data: weather is ‘exceptional’ if it exceeds the long-term average for the site location (typically based on 10 or 30 years of records) by a statistically significant margin. The Society of Construction Law’s Delay and Disruption Protocol guidance recommends comparison with the 10-year average for the month in question.

Under FIDIC Red Book 2017, Clause 8.5(b) entitles the contractor to an extension of time for ‘exceptionally adverse climatic conditions’. Clause 19 (Exceptional Events) may also apply to extreme weather events. Again, the financial risk of weather delay is borne by the contractor under the standard FIDIC allocation.

Under NEC4, Clause 60.1(13) defines a weather compensation event as weather measured at the weather data point identified in the contract that is shown by the weather data to occur on average less than once in ten years. This is a precise, defined threshold — and it entitles the contractor to both time and cost adjustment (unlike JCT and FIDIC).

Practical Application

For contractors: establish a weather monitoring system from the first day of the project. Record daily weather data — temperature, rainfall, wind speed — from a suitable on-site or nearby weather station. Compare this data against the 10-year meteorological records for the location at the end of each month. Identify exceeding events and calculate their impact on the critical path. Submit EOT notices promptly.

For employers and contract administrators: assess weather EOT claims against the historical meteorological data, not just the contractor’s assertion that weather was bad. Require the contractor to submit contemporaneous weather records and a comparison with historical averages.

Risks

For contractors: failing to maintain contemporaneous weather records makes it impossible to substantiate a weather EOT claim after the fact. Meteorological data is publicly available — a contractor without its own records is in a weak evidential position. For employers: automatically rejecting weather EOT claims without proper analysis may expose the employer to time-at-large arguments if weather events are severe enough.

Mitigation

Install an on-site weather station from the start of the project. Record data daily. Compare against 10-year averages monthly. Submit EOT notices for qualifying weather events without delay. Under NEC4, monitor against the contractually defined weather data point and threshold rigorously.

Conclusion

Weather delays are real, but the entitlement is specific and limited. Contractors who want to recover time for weather delays must demonstrate exceptionality against historical data, prove critical path impact, and follow the notice procedure. The financial risk, under most standard forms, remains with the contractor — regardless of how exceptional the weather was.