Three numbers run your July: 80 degrees, 95 degrees, and a quart an hour

It is the last week of June and you are looking at a five day framing week in Fresno starting Monday. The forecast has three digits in it by Wednesday. You have six people, a new laborer who started last week, a site with no trees on it and a schedule that does not care.

This is the standard where California is furthest from everywhere else. There is no federal heat rule to fall back on, so nothing you learned in another state applies, and Cal/OSHA enforces this one hard in construction because construction is named in the text of it. The good news is that the whole thing runs off the forecast, which means the entire week is plannable on the Thursday before it. Not reactable. Plannable.

Here is what each temperature triggers, what the water arithmetic actually comes to, and a real July week costed out day by day.

The temperature ladder

Everything in the outdoor standard hangs on the temperature at the work site, and it steps up twice (8 CCR 3395).

Two things about that table catch contractors out. The first is that 80 is not a high temperature in most of California, so on a great many working days shade is a hard requirement rather than a courtesy, and a pop up canopy in the truck is the cheapest compliance you will ever buy. The second is that shade means shade for everybody at once during a break, not a strip of it behind the gang box.

The quart an hour, turned into coolers

The water rule is one quart per employee per hour for the whole shift (8 CCR 3395). That is a number you can multiply, and multiplying it is the difference between a site that runs out at two in the afternoon and one that does not.

One quart an hour is two gallons per person across an eight hour shift. Run the Fresno crew: six people, on site 6:00 am to 4:30 pm with a half hour for lunch, so ten hours on the clock. Six times ten is 60 quarts, which is 15 gallons, which is three full five gallon coolers on site at the start of the shift with a plan to re-ice at lunch. Over the five day week that is 75 gallons.

Nobody buys 75 gallons of water by accident. It is a Friday afternoon decision, made before the week starts, and it is the single most common finding on a hot day inspection because it is the one that runs out rather than the one that was never there.

The water also has to be free, and it has to be close enough that drinking it does not cost somebody a walk across the site. A cooler by the gate on a 200 foot pour is technically water and practically not.

What changes at 95

High heat procedures switch on at 95 degrees, and they are four specific things rather than a general instruction to be careful (8 CCR 3395):

• Effective observation and monitoring. One supervisor watching 20 or fewer employees, or a mandatory buddy system, or regular contact by radio or phone with anyone working alone.
• Somebody designated to call emergency services, with the authority to do it and without needing to find you first.
• Reminders to drink water through the shift, out loud, from the supervisor.
• A pre-shift meeting covering the high heat procedures, the water, and the crew's right to take a cool-down rest.

That last one deserves its own paragraph. Employees are allowed and encouraged to take a preventative cool-down rest in the shade of at least five minutes whenever they feel the need, without asking permission (8 CCR 3395). Somebody on a cool-down rest gets monitored and asked whether they have symptoms, and does not go back to work while symptoms are still there.

Five minutes in the shade is not a productivity problem. A heat illness on a Wednesday afternoon costs the rest of the day, the crew that stops to help, the ambulance, the report to Cal/OSHA and the workers compensation claim behind it. The rest break is the cheap version of the same afternoon.

A real week, planned on the Thursday before

Take the Fresno job. The crew starts Monday 6 July 2026. Here is what the forecast turns into, with the five days before Wednesday averaging 87 degrees.

A heat wave under the standard is a predicted high of at least 80 degrees that is also at least 10 degrees above the average high of the preceding five days (8 CCR 3395). Wednesday clears both tests, and that is what makes it different from Thursday even though Thursday is hotter. The crew has not adjusted to it yet.

Acclimatization has a second date on it. A new employee is closely observed by a supervisor for their first 14 days (8 CCR 3395). The laborer who started Monday 6 July 2026 is inside that window through Sunday 19 July 2026, which covers this entire week and the next one. Write that date on the job file the day they start, the same way you write down their start date for the rest of the first hire paperwork.

Three planning decisions come straight out of that table, and all of them are free: the canopy goes on the truck Friday, the water order is placed Friday, and the Wednesday and Thursday starts move as early as the site allows. Heat planning that happens on the Thursday before is scheduling. Heat planning that happens on Wednesday at noon is an incident.

The plan is a document, and it can live where your other one lives

The heat rules also require a written Heat Illness Prevention Plan: in writing, in English and in the language understood by the majority of the crew, kept available at the worksite, covering the water, the shade, the high heat procedures, the emergency response and the acclimatization (8 CCR 3395).

It can sit inside your Injury and Illness Prevention Program rather than being a separate binder, which is the sensible way to do it, because it is the same document an inspector is already asking for and you have five business days to produce that one (8 CCR 3203). Building it once, properly, is covered in the IIPP guide for California contractors.

The emergency response part has one piece worth writing down properly. A rural site or a job on a county road needs clear directions for the ambulance, not just a jobsite name, and somebody on site who knows them. Emergency response that fails usually fails on the address rather than on the call.

Training happens before the work, for the crew and separately for supervisors, and the supervisor version includes what to do when somebody shows symptoms and how to get responders to the site (8 CCR 3395). It is a tailgate topic that fits neatly into the every 10 working days rhythm you already owe (8 CCR 1509), and the first hot week of the year is the obvious time to run it.

Inside a building is a different standard

The indoor standard applies from 82 degrees (8 CCR 3396), and control measures step up at 87 degrees, or at 82 where the crew is in clothing that traps heat or working in high radiant heat.

Construction hits this more than people expect. A tenant improvement in a sealed building with the HVAC off in August. An attic in July. A mechanical room. A garage conversion with the door down for dust control. A warehouse fitout. In every one of those the outdoor forecast is irrelevant and the temperature in the room is the number that matters, which means somebody has to actually measure it rather than guess.

Roofers get the worst of both, working on a surface far hotter than the air temperature the forecast quotes, which is worth understanding before you price a summer reroof. The trade side of that is in the C-39 roofing guide.

Put the hot weeks in the price, not in the schedule slip

None of this is expensive. A canopy, three coolers, ice, an earlier start and five minute rests. What it costs is time, and time is the thing that quietly comes out of your margin when a July week takes six days instead of five.

So price it. A summer week in the Valley is not the same production rate as an October week, and a contractor who bids both at the same rate is donating the difference. Put the real July output into your labor hours, then run the result through the markup and margin calculator, which is free and needs no signup. The full build of a rate that survives a hot month is in what to charge as a California contractor.

The other cost is the one you avoid. A heat illness becomes a workers compensation claim, an experience modifier and, if it is serious, an 8 hour phone call to Cal/OSHA (8 CCR 342). That side of the ledger is in workers comp for a California contractor.

Read the forecast on Thursday

Everything in this standard is knowable before the week starts, which is the whole advantage of it. The forecast is public. The thresholds are fixed at 80, 95 and 82. The water arithmetic is one multiplication. The 14 day acclimatization window is on your new hire's start date already.

The foreman who checks Thursday's forecast and orders water, ice and a canopy is running a normal week. The one who finds out on Wednesday morning is running a rescue. Same crew, same job, same weather.

On AEC Stack there is no monthly subscription. The platform fee is 2.5 percent of each invoice processed through the platform, so the job file that holds your crew, your hours and your hot week actuals is paid for by the jobs that get paid.

Pull up next week's forecast for your worst site, count the days above 95, and order the water today. Then open a working business file and put the real summer hours against the job, so next year's July bid is built on what the last one actually took.