Are heat illness claims covered by workers' compensation?

Yes. A heat-related illness that arises from job conditions is generally compensable, and a serious case with lost time behaves like any other lost-time claim on your worksheet. That matters because heat illness claims rise at least sevenfold on days above 90 degrees (WCRI, December 2024), and construction accounts for 21% of them, so the summer exposure is concentrated exactly where mods are already sensitive.

Why does one heat claim affect my mod for three years?

Experience rating uses a rolling window that typically spans three complete years, excluding the most recent policy period. A lost-time heat claim enters that window and stays until it ages out. Because its first dollars sit in the primary loss layer, which NCCI weights fully, the claim keeps pressure on the mod across every renewal in the window, not just the year it happened.

What is the primary loss layer?

NCCI splits each claim at a split point, recently moved from a flat $18,500 to state-specific values from about $15,000 to $25,000 (NCCI, 2024). Dollars below it are primary losses and count fully in the mod. Dollars above it are excess and are heavily discounted. A lost-time heat claim easily clears the split point, so its full primary portion drives the mod.

Does a heat prevention program actually lower my premium?

Not directly. A prevention program lowers premium by keeping avoidable lost-time claims out of the primary loss layer, where the mod does its damage. On a $50,000 manual premium, a mod pushed from 1.00 to 1.10 costs roughly $5,000 a year for three years. Preventing one such claim protects that money, plus the schedule credit a clean file earns.

Field ReportJuly 17, 2026 · 3 min read

Heat Illness Experience Mod: The Three-Year Cost

Heat illness claims rise at least sevenfold above 90 degrees, and construction takes 21% of them. One lost-time case sits in the primary loss layer for three rating years, moving a $50,000 account by real money.

By TraciThe Orson Group

Field Report

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Rise in heat-illness claims on days above 90 degrees

WCRI, December 2024

At a glance

A single lost-time heat claim is an experience mod problem for three rating years, not a one-summer safety line item. Heat illness claims rise at least sevenfold above 90 degrees (WCRI, December 2024), and construction absorbs 21% of them. On a $50,000 manual premium, a mod pushed from 1.00 to 1.10 costs roughly $5,000 a year until the claim rolls off.

Every July the heat memo goes out. Water, shade, rest, a buddy system. It reads like a moral obligation, and it is one. It's also the wrong frame for the person who signs the premium check.

Heat illness is an experience mod problem before it's a safety slogan. The slogan lasts a summer. The claim lasts three rating years.

The frequency spike is real, and it's dated

This isn't a soft trend. The Workers' Compensation Research Institute (WCRI) found heat-related illness claims rise at least sevenfold on days above 90 degrees compared with days in the 75 to 80 degree range, and as much as 18 times above 100 degrees (WCRI, December 2024). Construction absorbs 21% of all heat-related illness claims, more than any other industry (WCRI, December 2024). Roughly 75% of them land between June and August.

"These findings are especially significant amid ongoing policy debates on heat standards at the state and federal levels," said Sebastian Negrusa, WCRI's vice president of research (WCRI, December 2024). That debate is loud right now. Cal/OSHA issued a fresh heat advisory in July 2026 as temperatures climbed past 90 degrees. OSHA's National Emphasis Program on heat escalates inspections at an 80-degree heat index and again at 90 (OSHA, 2026). Georgia's HB 1071 would require heat illness prevention programs by 2027 or 2028 depending on employer size (WorkCompCentral, 2026). NCCI (the National Council on Compensation Insurance) flagged heat among the issues reshaping the 2026 workers' comp landscape.

All of that is the safety conversation. None of it is the premium conversation.

Why one claim outlives the summer

Here's the mechanic most toolbox talks skip. Your experience mod (EMR, the Experience Modification Rate) doesn't weigh every claim dollar equally. NCCI splits each claim into a primary layer and an excess layer at a split point that recently moved from a flat $18,500 nationwide to state-specific values ranging from about $15,000 to $25,000 (NCCI, 2024). The primary layer counts dollar-for-dollar in the mod formula. The excess layer is heavily discounted.

That design is exactly why a heat claim stings. A lost-time heat stroke case with a hospital stay and a few weeks off work clears the split point easily. Its first roughly $19,000 lands in the primary layer at full weight, and it stays in your experience window for three rating years. A medical-only claim would get discounted. A lost-time claim does not.

The heat illness experience mod math

Run the dollars on a small contractor. Say $50,000 in manual premium. On that base, every 0.10 the mod moves is about $5,000 a year. One lost-time heat claim that pushes the mod from 1.00 to 1.10 costs roughly $5,000 a year for the three years it sits in the window. That's $15,000 from a single avoidable claim.

The mod isn't the end of it. The carrier's loss cost multiplier already sits on top of the rate, so the loss reaches premium amplified, not at face value. And the schedule credit an underwriter extended when your file looked clean, often 10 to 15%, is the first thing to quietly disappear at renewal once a serious claim posts. Stack the mod, the multiplier, and the lost credit, and one heat case moves a $50,000 account by several thousand dollars a year.

That's the number the July memo never mentions.

What an audit would check

An audit checks whether the heat claims already on your worksheet are sitting where they belong. That means confirming a heat case is coded to the right classification and the right injury type, that its reserve still reflects reality rather than a cautious early estimate, and that no claim lingers in the experience window past the three years it's owed. A single lost-time heat claim carrying an inflated reserve can hold the mod elevated long after the worker returns. Most contractors never see the layer it's sitting in.

The prevention program is worth running for its own reasons. But the reason it pays back on the premium line is that it keeps claims out of the primary layer, where the mod does its damage. Before this renewal, send us your NCCI worksheet and we'll review it for free.