Heat doesn't stop a job the way lightning does — it degrades a crew hour by hour until someone goes down. Know the thresholds, and schedule around them.
| Heat index | Risk | Practice |
|---|---|---|
| 80–90°F | Fatigue on long exposure | Water available, normal rotation |
| 90–95°F | Heat cramps/exhaustion possible | Scheduled water breaks, shade, monitor new workers |
| 95–103°F | Heat exhaustion likely on heavy labor | Mandatory rest cycles, move heavy work to morning |
| 103°F+ | Heat stroke danger | Reschedule heavy outdoor work; emergency plan ready |
Your job site is hotter than the forecast. Roof decks in sun add roughly +13°F over ambient heat index; attics add far more; PPE and exertion add their own load. CrewCast bakes the roof-sun adder into roofing and solar scores and paces every heavy-labor trade by heat index, not air temperature.
Water, rest, shade; acclimatize new and returning workers over 1–2 weeks (most heat deaths happen in a worker's first days); train the crew to spot confusion, staggering, and dry skin — and treat heat stroke as a 911 call, cooling the worker immediately.
Above about 95°F heat index, heavy outdoor labor needs mandatory rest cycles; above 103°F, heat stroke risk makes rescheduling heavy work the right call. Exertion, sun, and PPE push effective risk higher than the number.
Direct sun on a roof deck adds roughly 13°F over the ambient heat index, so a 90°F forecast is a ~103°F roof. CrewCast's roofing score uses the roof-surface estimate, not the air number.
Building heat tolerance gradually — OSHA recommends new or returning workers ramp from ~20% exposure upward over 1–2 weeks. Most serious heat illness hits workers in their first week.
Yes — NWS heat advisories arrive as push alerts for saved locations, and every trade score deducts for dangerous heat-index hours.