Safety and field operations

How to plan for weather on construction projects

Plan for normal weather in the schedule and the price, set clear stop-work triggers for dangerous weather, protect materials and finished work, and document every weather day the same day so delay claims hold up.

Two construction professionals review paper plans beside a tablet at a jobsite workbench.
Plan reviews connect field conditions, drawings, and the next decisions on a job. AI-generated illustration.

To plan for weather on a construction project, start with the history for the job's location and season, build the expected number of lost days into the schedule, and sequence weather-sensitive work (excavation, concrete, roofing, exterior finishes, crane picks) for the best months you can. Then write stop-work rules for lightning, high wind, heat, and cold, check the forecast in the morning and at midday, protect materials and finished work before storms, and record weather and its impact in the daily log every day. Contracts usually treat normal weather as the contractor's risk and only unusually severe weather as excusable, so read the clause before you bid.

Weather in the contract and the schedule

Most weather fights come down to one question: was this weather worse than normal for this place and month? Many contracts give time, but not money, for unusually severe weather that actually delayed critical work. Some list a number of anticipated weather days per month. Some say nothing and leave it to the general delay clause. Know which you have before you set the schedule. See weather delay and how to handle weather delays in the schedule.

Historical data helps here. NOAA's National Centers for Environmental Information publishes climate normals and station records you can use to estimate typical rain, snow, and temperature days for the job location. The current official normals are 30-year averages for 1991 to 2020, drawn from almost 15,000 U.S. stations, and cover temperature, precipitation, and snowfall by month and by day. Use the nearest station with a long record, not a regional average, and remember that normals tell you what is typical, not what this year will bring.

How to plan for weather in 7 steps

  1. Read the weather clause. Note what counts as excusable, notice deadlines, and any built-in weather days.
  2. Pull the history. For each month of the job, estimate how many days usually lose work to rain, snow, extreme heat or cold, or wind for the work you will be doing then.
  3. Build weather days into the schedule. Add them to the activities that are actually weather sensitive, or as a separate weather allowance, and show it clearly in the baseline schedule.
  4. Sequence around the season. Push to get dried in before the wet season. Avoid pouring slabs in the coldest weeks if you can. Plan exterior work for the months with the fewest lost days.
  5. Set stop-work triggers. Write down who decides, and the rule for lightning, wind, heat, and cold, so the call does not depend on who is in charge that day.
  6. Protect work and material. Tarps, heaters and blankets for concrete, drainage around excavations, covered storage, and tie-downs for loose material and roofing.
  7. Document daily. Record conditions, hours lost, crews sent home, and which activities were affected in the daily log, with photos. Send any notice the contract requires on time.

Stop-work rules for dangerous weather

Weather hazards and the rules or guidance behind them
HazardRule or guidanceSource
LightningNo safe place outside when thunderstorms are in the area. When thunder roars, go indoors. Wait 30 minutes after the last thunder or lightning before going back out. Safe shelter is a substantial building or hard-topped vehicle; small sheds and open vehicles are not safeNational Weather Service
Scaffolds in storms or windWork on or from scaffolds is prohibited during storms or high winds unless a competent person decides it is safe and workers are protected by fall arrest or wind screens29 CFR 1926.451(f)(12)
Snow and ice on scaffoldsNo work on scaffolds covered with snow, ice, or other slippery material except to remove it29 CFR 1926.451(f)(8)
CranesThe competent person must adjust equipment or operations for the effect of wind, ice, and snow on stability and rated capacity29 CFR 1926.1417(n)
ColdSchedule cold jobs for warmer months or warmer parts of the day, provide warm break areas and warm liquids, use relief workers, and monitor workersNIOSH
HeatWater, rest, shade, and acclimatization for new workers; some states have heat standardsSee heat illness guide

Add after-storm checks. Scaffolds must be inspected by a competent person before each shift and after any event that could affect their integrity, and excavations, fencing, erosion controls, and temporary power should all be walked after heavy rain or wind before crews go back to work. For hot weather, see heat illness prevention on construction sites.

Worked example: a fall start on a two-story building

Say a general contractor is starting a two-story, 14,000 square foot office in mid-September with a 9-month schedule. The site superintendent pulls local history and estimates weather days for exterior work as an example: September 2, October 3, November 5, December 7, January 8, February 7. Interior work after dry-in is barely affected.

  • Goal: get the building dried in by mid-December, before the worst months. That means foundations in September, framing and sheathing in October and November, roof by early December.
  • Weather allowance: the exterior activities in that window carry 17 weather days (2 + 3 + 5 + 7). The schedule shows them as weather days inside each month's work, not hidden float.
  • Concrete plan: slab on grade poured in October, with blankets and heaters priced into general conditions for any pour after mid-November.
  • Triggers: lightning policy in the site safety plan; the steel erector's crane plan states its wind limits from the manufacturer's chart; scaffold work stops in high wind unless the competent person clears it.

If November brings 9 lost days instead of 5, the super has a record showing the difference, the activities affected, and that the work was on the critical path. That is the start of a valid time extension request, not an argument after the fact.

Mistakes to avoid

  1. No weather days in the schedule. Then every normal rainy day looks like a delay you caused.
  2. Claiming normal weather as a delay. Most contracts only excuse unusually severe weather.
  3. Vague daily logs. "Rain" is not enough. Record hours lost, crews sent home, and which work could not proceed.
  4. Letting the crew decide on lightning one storm at a time. Use a written rule and enforce it the same way every time.
  5. Not protecting installed work. Water damage to finished work is often your cost to fix, even if the storm itself was excusable.

Templates and tools that help

Use a construction schedule template with weather days shown, update the three-week look-ahead against the 10-day forecast, and log conditions daily with a construction daily report template. For claims, read how to document construction delays for claims.

Smart Business Automator keeps the daily logs, photos, and schedule changes for each job together, and its daily log summaries can pull a list of weather days and affected activities when you need to request time. See construction workflow automation.

Frequently asked questions

How many weather days should I add to a construction schedule?

Base it on historical weather for the job location and the months when weather-sensitive work happens. Some contracts set the number of anticipated weather days per month, in which case use those.

When should a construction crew stop work for lightning?

The National Weather Service says there is no safe place outside when thunderstorms are in the area. When thunder is heard, move to a substantial building or hard-topped vehicle and wait 30 minutes after the last thunder or lightning before going back out.

Can you work on scaffolding in high winds?

OSHA prohibits work on or from scaffolds during storms or high winds unless a competent person determines it is safe and workers are protected by a personal fall arrest system or wind screens.

Are weather delays excusable in construction contracts?

Often only when the weather was unusually severe for the location and time of year and actually delayed critical work. Many contracts give time but not money for these delays. Read your contract's weather and delay clauses.

Sources

  1. National Weather Service: Lightning safety overview
  2. 29 CFR 1926.451: General requirements for scaffolds (Cornell LII)
  3. 29 CFR 1926.1417: Operation of cranes and derricks (Cornell LII)
  4. NIOSH: About cold stress
  5. NOAA National Centers for Environmental Information: U.S. climate normals
Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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