Weather Day
A day of lost work time caused by weather conditions that prevent safe or effective construction, commonly used as the basis for a contractor's request for additional contract time, though usually only when the weather is unusually severe compared to the historical average for that location and time of year.
Why it matters
Most construction contracts allow schedule extensions for "abnormal" weather, but not for ordinary weather a region should expect: a rainy week in a rainy climate typically isn't grounds for extra time on its own. Whether a weather day actually qualifies for a schedule extension depends on comparing it against historical weather data for the site, not just whether work stopped.
On a real project
A contract in a region with a well-documented average of six rain days in April allows a schedule extension only for rain days beyond that average. A project experiences eleven rain days that April, and the contractor documents and claims a five-day extension for the days beyond the historical norm.
Who this matters most to
A Superintendent logs weather conditions and their impact on the day's work in the daily report, since that documentation is what a weather day claim depends on later. A Scheduler tracks weather days against the contract's allowance and factors legitimate extensions into schedule updates.
Where this goes wrong
A superintendent doesn't bother logging weather conditions on days when work slows down but doesn't fully stop, assuming it won't matter later. Months later, when the project is behind schedule and the contractor wants to claim weather-related time extensions, there's no daily report documentation to support which specific days were actually lost to weather versus other causes.