Is a Weather Metric record enough for a claim on its own?

It is a record of conditions from named public sources. Whether an event qualifies, and what it is worth, is decided through the contract, usually with the project’s own records beside it.

Which weather station should an NEC4 record use?

The one stated in the Contract Data. Where none is stated, the record names the nearest gauge and its distance, so the choice is visible.

What does once in ten years mean in practice?

Roughly the value exceeded in that calendar month in one year out of ten at that place. The record shows it from thirty years of reanalysis for the same month.

Weather Metric › Weather delay claim evidence

What does a contemporaneous weather record need to contain under NEC and JCT?

Weather is one of the most argued causes of delay. Whether it is a compensation event under NEC or a Relevant Event under JCT, the argument turns on contemporaneous records that say what the weather was, where it was measured and how unusual it was.

Under NEC4

Clause 60.1(13) makes weather a compensation event when a weather measurement recorded within a calendar month, at the place stated in the Contract Data, is shown to occur on average less frequently than once in ten years. The measurements usually named are cumulative rainfall, the number of days with rainfall over 5 mm, the number of days with a minimum air temperature below 0 degrees, and days with snow lying. A record therefore needs monthly figures for the right place, and a reference for what once in ten years means there.

Under JCT

The JCT Standard Building Contract lists exceptionally adverse weather conditions among the Relevant Events for an extension of time. There is no fixed test, so the record has to show both what happened and why it was exceptional for the time of year and the place.

What the record should hold

Daily figures, dated, for the site’s location. Measured rainfall where there is a gauge, with the station named and its distance from the site. Modelled temperature, wind and gusts, labelled as modelled. The comparison with the long-term figures for the same month at the same place. Daylight, because lost light is its own argument in winter.

How Weather Metric builds it

The Record tab gives each of those for any range: Environment Agency gauge rainfall, modelled conditions, daylight and lost-light minutes, and a monthly comparison with thirty years of ERA5 reanalysis (1991 to 2020) that shows the once in ten years value for the place. Export it as a CSV or print the dated record from the browser.

Weather Metric reports the conditions. Whether an event qualifies, and what it is worth, is for the contract’s own process.

Questions people ask

Is a Weather Metric record enough for a claim on its own?: It is a record of conditions from named public sources. Whether an event qualifies, and what it is worth, is decided through the contract, usually with the project’s own records beside it.
Which weather station should an NEC4 record use?: The one stated in the Contract Data. Where none is stated, the record names the nearest gauge and its distance, so the choice is visible.
What does once in ten years mean in practice?: Roughly the value exceeded in that calendar month in one year out of ten at that place. The record shows it from thirty years of reanalysis for the same month.