When weather hits the programme, the argument comes down to records. Enter your site postcode and the period in question — get rain days, frost days and wind against the 10-year average for that exact location, as a print-ready record you can attach to a delay notice.
Why records matter
JCT contracts allow extensions of time for “exceptionally adverse weather”; NEC compares conditions against 1-in-10-year weather data. Either way, the conversation starts with what actually happened on site versus what's normal for the time of year — which is exactly what this record shows.
What this is (and isn't)
Data comes from the ERA5 reanalysis dataset at the nearest model grid point to your postcode — a consistent, independent source, but not a Met Office station record. Whether conditions meet your contract's test is a contractual question; this tool gives you the factual starting point, not advice.