On civil work, weather is not an occasional problem. It is the main variable. Earthwork, compaction, paving, liner placement, pipe installation in open trench: all of it stops when the ground is too wet, too frozen or too hot, and some of it cannot restart until conditions recover.
Most public contracts treat unusually severe weather as an excusable delay: the contractor gets time, though usually not money. But the time is rarely automatic. The contractor has to show that the weather was worse than the contract anticipated, and that it delayed work on the critical path. Both of those are schedule questions.
What the contract usually says
Contracts handle weather in one of two ways, and the schedule has to match whichever one applies.
Anticipated weather days. Many public specifications list the number of working days per month the contractor should expect to lose to weather, often from historical records for the project location. The contractor builds those days into the baseline. Only days lost beyond that number support an extension.
Weather calendar. Other contracts expect the schedule's calendars to carry the anticipated weather, with work days removed in the wetter or colder months.
Either way, the baseline is where the weather allowance is set. If the baseline ignores it, the first wet month puts the job behind on paper and the contractor has no allowance to measure against.
What has to be recorded, as it happens
The strongest weather extension requests are built from records kept month by month, not reconstructed at the end:
- Daily reports that state whether work was stopped or reduced by weather, which crews and which activities were affected, and the conditions (rainfall, temperature, ground condition).
- Recovery days. On earthwork, one heavy rain can stop work for days afterward while the site dries out. Those days count, but only if they are recorded with the reason.
- The monthly update. Each update should record the weather days lost in the period, compare them to the contract allowance, and show the effect on the critical path.
Showing the delay was critical
A day lost to weather only extends the contract if it delayed critical work. If rain stopped the paving crew but paving had a month of float, there is no extension. If rain stopped mass excavation that was driving the job, there is.
That is why the schedule matters. With the weather days recorded in each update, the analysis is straightforward: the days lost in excess of the allowance, on activities on the critical path, in that period. Without the updates, the contractor ends up arguing from daily reports alone and the owner's reviewer asks which of those days actually moved the job.
Seasonal and permit windows
Civil work also runs into windows the contractor does not control: in-water work windows, wet-season grading restrictions, environmental timing restrictions and paving temperature limits. When a delay pushes work out of its window, the effect can be months, not days. A schedule that carries those windows as constraints shows that effect clearly. A schedule that does not will show a small slip that later becomes a large one with no explanation.
Where CPM Pros fits
CPM Pros builds and updates Primavera P6 schedules for civil and public works general contractors, including landfill, utility and site work. We build the contract's weather allowance into the baseline, record weather days in each monthly update, and prepare the time impact analysis when excess weather delays the critical path. The work is fully remote.
Send the specification section on scheduling and weather, and we will send back a written quote, typically within 3 business days.