Weather costs in an outdoor site bid come from runoff, heat, and storms, and they touch nearly every line. Rain turns a cleared pad into a sediment problem. Heat slows the crew and forces more breaks. A storm can stop a job for an afternoon or for a week. Estimators who treat these as a general contingency often find out during the job, when the margin is already gone.
This post covers three weather-linked items, in the order you are likely to meet them on a site walk and through the schedule: runoff on the ground, heat on the crew, and storms that stop the work. For each one I point to the official source behind the claim and keep everything else general. Your local permit office, your insurer, and your own safety program set the real requirements for your job. Use these notes as a checklist of what to ask and what to price.
1. Price the runoff controls during the site walk
Start the site walk by following the water. Stormwater is the water that runs off a site instead of soaking in. The EPA's NPDES stormwater program page puts it this way: "Stormwater runoff is generated from rain and snowmelt events that flow over land or impervious surfaces, such as paved streets, parking lots, and building rooftops, and does not soak into the ground."
On an outdoor site, impervious surfaces include existing pavement and the roof of a site trailer. Each one sends water somewhere. That somewhere is often a storm drain, a neighbor's lot, or a low spot on your own site that fills during a heavy rain. Mark those paths on the walk. For the measuring itself, see Site walk measures: 3 checks before the takeoff. Note where the water leaves the property line and whether any drain near the work connects to a public system.
The same EPA page explains that the program regulates some stormwater discharges from three potential sources: municipal separate storm sewer systems, construction activities, and industrial activities. Ask the permitting authority which permit applies and what it requires before you finalize the scope. Do not carry over the requirements from your last job without checking them.
Next, price the controls. The EPA's stormwater program page calls them best management practices, or BMPs, and says: "To protect these resources, communities, construction companies, industries, and others, use stormwater controls, known as best management practices (BMPs)." The same page notes that "These BMPs filter out pollutants and/or prevent pollution by controlling it at its source." For a bid, that becomes a checklist that mixes items you can measure from the plan with items you have to estimate from experience:
- Perimeter sediment barriers, such as silt fence or wattles, along low edges and around stockpiles.
- Inlet protection on any storm drain near the work.
- A stabilized entrance where trucks leave the site, so mud does not get tracked onto the road.
- Covers or berms for stockpiles and bare soil.
- Temporary seed, mulch, or erosion blanket on areas that will sit exposed for a while.
- Inspection hours and a cleanup allowance for sweeping mud off paved surfaces.
- A temporary sediment basin if the grading is large enough that barriers alone will not hold the water.
A worked example helps. Suppose a grading job sits on a slope that drains toward a storm inlet at the bottom of the road. The plan shows silt fence along the low edge, which is a clean quantity. The walk shows the inlet is only a few steps from the stockpile, and the entrance is a gravel pad that will turn to mud within a day of rain. The estimate that follows adds inlet protection, a stabilized entrance with a larger gravel quantity, and a cover for the stockpile. It also adds a repair allowance for the rainy weeks in the schedule and a line for road sweeping. None of these items is on the drawing. All of them come from the walk.
Quantities from the plan are the easy part. Rain adds cost in two other ways. First, a heavy storm can knock down a run of silt fence, fill a basin, or wash out a berm, and someone has to fix it before the next rain. Put a repair allowance in the bid, sized to the rain season you expect, and say in the scope how repairs will be paid. Second, time adds cost. Plan to keep controls on exposed ground in service as long as the ground stays open, and confirm the actual requirement with the permitting authority or the contract. If the owner's schedule slips and the grading sits through another month, the mulch, inspections, and maintenance run for that month too. Ask for the planned exposure period in writing and price the maintenance for that period, not for the shorter period you would like.
Finally, settle who pays for mud on public roads and who pays for a fine or a stop-work order caused by a control failure. These are often the most expensive weather items, and they are easy to leave out of a bid. If the scope is silent, read the contract to see where that risk lands. If you exclude it, write the exclusion clearly and tell the owner what it means for them.
Before the first machine moves in, document the site. Take dated photos of the existing drainage, the edges of neighboring property, the road condition at the entrance, and any standing water. If mud or runoff reaches a neighbor later, that record is what separates a fault in your controls from damage that was already there. The cost is a few hours of walking and photographing, and it belongs in the mobilization line.
2. Plan heat controls into the crew schedule
Heat changes the crew before it changes the equipment. The Minnesota Department of Labor and Industry's heat stress guidance is a state workplace-safety source, but its basic point holds wherever people work outdoors in warm weather: "The two most important methods of preventing heat disorders are hydration and acclimatization because they increase the ability of the body to tolerate heat stress."
Hydration is the cheap part of that sentence, and the one that is easiest to underprice. It means water on site in quantity, cups or bottles, cool storage, and someone whose job includes refilling the supply. Price it for each crew-day and scale it to the hot weeks in the schedule, not to an average month.
Acclimatization is the part that changes production. A crew that has not worked in heat for weeks will not perform like a crew that has been out in it all summer. Consider a crew of four moving onto a site after a cool spring. On the first hot afternoon they cannot match the output they bid for the cool weeks. An estimator who priced a ramp-up for the first hot days, with lower output, more supervision, and more frequent breaks while workers build tolerance gradually, can explain the difference to the owner and show that it was planned. If you are bringing in new hires or a crew from a cooler region, the ramp-up cost is bigger.
The same guidance adds: "Engineering and administrative controls are important in reducing heat exposure." That sentence gives you two kinds of cost to separate in the bid.
Engineering controls are physical. They include shade over break areas, fans or misting where the site allows, cooling stations, and rest areas placed near the work instead of across the site. They are equipment and materials, so they belong in the general conditions or site logistics section, with a rental or purchase price and a set-up and tear-down time.
Administrative controls are scheduling decisions. They include starting earlier in the day, moving the heaviest tasks into cooler hours, adding scheduled breaks, and rotating people off the hottest jobs. These costs are mostly labor. An earlier start can mean a longer day, a shifted shift, or premium time under the crew agreement. Lower output per hour means more hours for the same work. Build these into the schedule as a productivity factor for hot days, and say in the bid what that factor is based on.
Temperature alone is a weak guide because humidity changes how hot a day feels. The Canadian Centre for Occupational Health and Safety gives a worked example in its humidex page: "For example, if the temperature is 30°C and the relative humidity is 70%, the humidex rating is 41." If your job is somewhere else, use the heat measure your local agency publishes. The principle is the same either way: a dry 30 degrees and a humid 30 degrees do not put the same load on the crew.
The same page says: "If the reading is in the mid to high 30s, then you should tone down or modify certain types of outdoor exercise, depending on the individual age and health, physical shape, the type of clothes worn and other weather conditions." That passage is about outdoor exercise, not construction, so use it as a warning sign, not as a production rate. It does tell you what to check: the age and health of your crew, what they wear, and what the rest of the weather is doing. Heavy protective clothing raises the load compared with light clothing. A crew in full protective gear working in the mid to high 30s on the humidex needs a different plan from a crew in light clothes at the same reading.
Sequence matters on hot days. Put the most physically demanding tasks, such as hand digging, lifting, and work in full protective gear, into the cooler early hours. Schedule the work that can be paused, such as material staging, inspections, and layout, for the afternoon. If the job includes concrete or asphalt placement, check the temperature limits in the specification and the supplier's instructions before you bid a summer pour, because those limits can decide the work window. Night work brings its own costs, including lighting, power, possible noise limits, and a supervisor who stays on shift.
Keep a simple log of heat conditions and breaks on each hot day. The log shows the owner why output dropped, and it gives you real figures for the productivity factor on the next bid. For the crew-hour side, see Heat checks: 3 costs to include in crew hours.
Two cost notes close this step. First, the forecast for the bid window matters. An estimate built on a cool spring forecast, for a job that runs into August, will carry heat costs the bid never included. Second, heat and rain often arrive together. When they do, the runoff costs from step 1 and the heat costs from this step run at the same time. Do not price them as separate contingencies that can never overlap.
3. Write the storm shutdown plan and price the idle time
Storms stop work in two ways. The work itself becomes dangerous, and the crew has to move to safety. The CCOHS lightning page gives the scale of the risk: "A lightning bolt is a million times more powerful than household current, carrying up to 100 million volts of electricity." Few outdoor site tasks can be done safely under that kind of hazard, so the plan for when to stop has to be written before the storm arrives, not improvised during it.
The same page warns about distance: "Lightning can strike as far as 16 kilometres outside of rainfall areas." For estimators, this is the detail to remember. A crew that waits for rain to start before pausing can be caught by a strike from a storm that is still some distance away, or one that has already moved past the rain. The stop trigger should be based on the storm's approach and on lightning activity near the site, not only on whether it is raining over the work.
The page also states what the employer owes the crew: "Employers need to recognize the hazards associated with storms and, where appropriate, have safe procedures and work systems in place to minimize the risk of injury or harm to workers, and should review these policies seasonally." Two pricing consequences follow. The storm procedure is part of the job, so its planning time belongs in the bid. And the procedure is not a one-time document. Reviewing it during the season is a small, recurring cost that should appear in the project management or safety budget.
A storm procedure for an outdoor site usually covers several points, and each one has a cost or a time impact:
- Who has the authority to call a stop, and how that call reaches every crew and subcontractor.
- What counts as a stop, and what counts as safe to resume.
- Where people go. Identify a building or a substantial vehicle within a short walk of each work area, and price the time to get there. A crew at the far end of a grading pad may need a long walk.
- How the crew decides it is safe to resume, and who confirms it.
- What happens to equipment. Some machines must be parked in a set spot or moved, which adds time and sometimes a demobilization charge.
Before the storm arrives, someone has to secure the site. Loose materials, signs, temporary fencing, and light stands can become hazards in high wind, and a crew pulling them down during the storm is a crew at risk. Put a pre-storm walk into the stop procedure, and price the labor and the time it takes. For a job with cranes, scaffolding, or tall temporary structures, the securing steps belong in the lift and access plan, not in an afterthought.
Then price the idle time. Standby labor is often a major item, and how you pay for it depends on your crew agreements and the owner's contract. Equipment on standby may carry an idle rate, and a move to a safer location adds a mobilization cost. If you use a lightning detection service or a monitoring tool, add its subscription or rental cost, along with the cost of someone trained to watch it.
Schedule float is the other half. Add weather days to the schedule, and for each day carry the general conditions that run daily: site fencing, trailers, supervision, insurance, and utilities. Extra days also extend the runoff controls from step 1 and the heat controls from step 2.
Keep a record of each stop: the time it was called, the time work resumed, and who made the call. Owners ask for this when weather days are disputed, and it protects the crew as well. For the wait-time side, see Lightning wait costs: 3 times to log for each stop.
Last, check the contract for a weather-day clause. Estimators often price storm time carefully and then accept a contract that gives no relief for it. If the owner accepts weather days, define what counts, how they are documented, and how they are paid. If the owner does not, decide whether the risk is worth carrying, and price it accordingly. Whichever way it goes, the three items in this post belong in one estimate, because a single storm can start a stop, extend the runoff exposure, and push the crew back into the heat at the same time.
Related guides: Caltrans changed bid items: 2 payment routes · Public bid costs: 3 items to price outside unit rates · Abrasive wheel safety rules: 9 checks for site compliance.