Weather delay days: how contracts turn rain into a time extension

One U.S. state specification (Tennessee) shows the machinery: a monthly baseline, defined thresholds, the 50% rule and NOAA-backed monthly reports. How to document your weather days.

Every contractor knows weather costs days. Fewer know that a well-drafted contract counts those days with surprising precision. A weather delays specification used by the State of Tennessee shows the machinery: the contract sets a Standard Baseline — the normal number of calendar days each month when exposed construction is expected to stop, derived from NOAA climate data (for Tennessee: 15 days in January down to 5 in September). Days within the baseline are yours to absorb; only weather beyond it earns a time extension.

What counts as a weather day

• Defined thresholds: adverse weather means precipitation over 0.10 inches, temperatures below what the day's activity requires, or sustained wind over 25 mph — measurable conditions, not impressions.
• The 50% rule: a Weather Delay Day requires that conditions prevent work for 50% or more of the scheduled workday on critical path activities. Rain at 3 PM on a float-heavy day doesn't count.
• Dry-out days: mud after the storm counts too, at no more than one dry-out day per whole inch of excess precipitation — but only if the contractor took reasonable steps to keep access open.

The documentation decides

The same specification demands a monthly weather delay report — submitted every month, even months with no claim — supported by daily jobsite logs showing which critical path activities weather affected, plus actual data from the nearest NOAA station. The designer reviews, signs, and the accepted days accumulate toward a single change order at substantial completion. The pattern is universal: the extension is won by the contractor whose daily reports already recorded the weather, the activity and the impact — and whose change order process turns accepted days into contract time.

Rain is weather; undocumented rain is your loss

Daily logs with weather, activities and impacts captured as the day happens — that's the evidence a time extension stands on, and it's the operation an ERP for construction companies runs for a contractor, implemented around the way each company works.