Heat Claims and Your EMR: What a 7x Surge Means This Summer
WCRI data shows heat-related illness claims jump sevenfold at 90°F. Construction takes 21% of those claims, and most land squarely in the primary loss layer that drives your mod.
Heat-related illness claims increase at least sevenfold when temperatures exceed 90°F and up to 18 times above 100°F (WCRI FlashReport, December 2024). Construction accounts for 21% of all such claims. Because most heat claims fall below NCCI's split point, they land entirely in the primary loss layer, where they carry full weight in your experience modification rate.
Ninety degrees isn't unusual on a Southeast jobsite in July. It's background noise. But the first dedicated study from the Workers Compensation Research Institute (WCRI) on heat-related illness claims puts a number on what that background noise costs, and what it means for your EMR (Experience Modification Rate, also called the mod). Heat claims don't just rise when temperatures climb. They multiply.
The study, published in December 2024, analyzed workers' comp claims across 31 states from 2013 to 2022. The headline: heat-related illness (HRI) claims increase at least sevenfold when temperatures exceed 90°F compared to days between 75°F and 80°F. Above 100°F, the increase reaches 18 times (WCRI FlashReport, December 2024). Seventy-five percent of those claims land between June and August.
Construction takes the largest share of heat claims
Of all industries tracked, construction accounts for 21% of heat-related illness claims (WCRI, 2024). Manufacturing takes 18%. Transportation and utilities take 15%. Together, those three sectors carry more than half the total. But construction's share is disproportionate to its workforce size.
Southern states compound the problem. WCRI's data shows southern states post 309 HRI claims per 100,000 total claims, the highest regional rate in the country. That's partly climate, partly the concentration of outdoor trade work, and partly a regulatory gap. No Southeast state has enacted a heat illness prevention standard. Florida preempted local governments from passing their own heat ordinances in 2024 (HB 433, April 2024). Georgia, Tennessee, Alabama, and the Carolinas rely entirely on federal OSHA enforcement under the General Duty Clause.
Why small heat claims hit your EMR harder than you'd expect
Here's the counterintuitive part. Heat claims are relatively cheap. The average compensable HRI claim runs under $2,000 (WCRI, 2024). Compare that to a fall or a struck-by injury that can reach six figures. On paper, a sub-$2,000 claim looks trivial.
It isn't. NCCI's (National Council on Compensation Insurance) experience rating formula splits every claim at a state-specific dollar threshold called the split point. Losses below the split point are "primary" losses; losses above it are "excess." Primary losses receive full weight in the mod calculation. Excess losses are discounted heavily.
A $1,900 heat claim falls entirely below the split point in every NCCI state. One hundred percent of it counts as primary loss. So does a $5,000 claim. So does a $15,000 claim in most states. For a contractor running $500,000 to $2 million in annual payroll, two or three additional primary losses in a single experience period can push the mod up 5 to 12 points. On $600,000 in annual workers' comp premium, 10 mod points adds $60,000 a year. That elevated mod persists for three years.
In our audits of Southeast contractor worksheets, heat claims are among the most common primary losses that go unexamined.
The regulatory pressure keeps building
OSHA updated its National Emphasis Program (NEP) on heat in April 2026, replacing the 2022 original with a five-year directive (CPL 03-00-024, OSHA, April 2026). The updated program targets 55 high-risk industries. Construction remains at the top of the list.
The shift isn't just administrative. Between 2022 and 2024, OSHA conducted roughly 7,000 heat-related inspections and issued more than 60 citations under the General Duty Clause (OSHA, April 2026). The new directive adds Appendix J, a standardized citation framework that simplifies the process for inspectors writing heat-related violations. The direction is clear: fewer warnings, more penalties.
An OSHA citation doesn't appear on your NCCI worksheet. But the incident behind the citation often generates a workers' comp claim that does. A contractor with multiple heat-related claims across two or three summers isn't just facing regulatory scrutiny. They're building a loss history that feeds directly into the mod calculation at the next renewal.
Frequency is the mod killer, not severity
The experience rating formula penalizes frequency more than severity. This is by design. NCCI's actuarial logic holds that claim frequency predicts future losses better than the size of any single event.
Heat claims tend to cluster. They appear in the same months, on the same project types, among the same crews. Two heat exhaustion claims in year one and one in year two don't look like bad luck to the formula. They look like a pattern.
For a mid-size contractor, each additional primary loss increases the actual primary losses on the worksheet while expected losses stay fixed. That ratio drives the mod above 1.00. A single severe fall can be partially absorbed by the excess loss weighting. Three small heat claims cannot.
What an audit would check
An audit would examine whether heat-related claims on the worksheet are coded correctly, whether any have been reclassified from lost-time to medical-only as the claimant returned to work, and whether reserves on open heat claims still reflect the actual medical outcome. Most heat illness claims resolve quickly. When the reserve doesn't come down to match, the inflated value sits in the mod calculation for up to three years.
If your experience period includes heat claims from prior summers, send us your NCCI worksheet and we'll show you what they're doing to your mod.