Live Tracker
The thermometer on the wall is not the number that kills. This page explains the number that matters — Wet Bulb Globe Temperature — and the two flag lines we judge a Texas workday by.
Fourteen Texas cities
This is the live half of the page: the current estimated WBGT for the big Texas population centers, read off National Weather Service forecasts as this page loads and judged against the same two lines above — plus the peak WBGT still ahead in today’s forecast, so a crew can see the worst of the day before it arrives.
Dallas
––°F WBGT
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Austin
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San Antonio
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Houston
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Lubbock
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El Paso
––°F WBGT
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Corpus Christi
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Brownsville
––°F WBGT
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Amarillo
––°F WBGT
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Midland
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Texarkana
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Beaumont
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San Angelo
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Wichita Falls
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Read these numbers honestly: they’re estimates
The WBGT figures this project uses are estimated from National Weather Service data — forecast temperature, humidity, wind speed, and sun and cloud cover — using standard WBGT estimation methods. They are not measured by a black-globe thermometer on the jobsite.
That cuts one way, not the other: an attic, a roof deck, or a trench can run far hotter than the forecast estimate for the area around it. Read the estimate as the floor, not the ceiling. If the estimate says a day crosses a line, the man in the attic crossed it further.
The two lines we use
The project judges every day — forecast or fatal — against the University Interscholastic League (UIL) WBGT flag thresholds. Two of those lines do most of the work:
79.7°F
The rapid-cooling threshold
Past this WBGT, hard physical work can push a worker’s core temperature up faster than shade, water, and rest breaks can pull it back down — exertional heat stroke becomes a live risk, not a remote one.
What it means on a jobsite: if a worker goes down on a day past this line, survival turns on rapid cooling — cold-water immersion on the spot, within minutes, before transport. Cool first, transport second. A site working past 79.7° with no way to cool a collapsed worker fast is gambling with the one emergency where minutes decide whether a man goes home or to the morgue.
89.8°F
The black-flag line
At this WBGT, the UIL stops outdoor activity outright — and so do we. Past this line, no schedule of water and rest breaks keeps a working body ahead of the heat it is gaining. The safety margin is gone.
What it means on a jobsite: the outdoor work does not happen. It gets rescheduled, moved indoors or into shade, or it waits for a cooler hour. A foreman who sends a crew up on a roof past the black-flag line isn’t being tough — he’s spending his workers’ bodies and calling it a work ethic.
What WBGT is — and why the regular temperature lies
Wet Bulb Globe Temperature (WBGT) is a single number that measures what the heat actually does to a working body. The air temperature on a weather app measures one thing: how hot the air is in the shade. WBGT folds in four: air temperature, humidity, wind, and the radiant heat of the sun — the “globe” in the name is a black globe that soaks up sunlight the way a roof deck, a dark uniform, or human skin does.
That difference is life and death because of how the body cools itself. Working muscles generate heat; the body dumps it by sweating, and sweat only works if it can evaporate. Humidity throttles evaporation. Direct sun adds heat load on top. Wind helps — until it doesn’t. So two days with the same 98° forecast can be completely different days for the person on the roof: still, humid Houston air at 98° is a far more dangerous shift than dry, breezy 98° in Lubbock. The temperature says they’re the same day. WBGT says they’re not. That’s why the military, OSHA’s heat guidance, and Texas school athletics under the UIL all run on WBGT instead of the thermometer.
The heat index is not a substitute, either: it’s calculated for a person standing still in the shade. Nobody in our archive died standing still in the shade.
Why we track it: the archive is drawn against these lines
This isn’t academic. The same WBGT math runs backwards through the archive: the case records carry WBGT estimates for the day each worker died, so every death can be judged against the same thresholds. Of the 58 cases with WBGT estimates, 46 died on days above the 89.8° black-flag line — days when, by the standard Texas uses for high-school athletes, the work should never have happened outdoors at all.
And the warning system didn’t catch them. Matched against the National Weather Service warning record, 30 of the 49 checkable cases died on days with no heat warning in effect for their county. The official alerts and the actual danger are two different things. WBGT is how we measure the actual danger.
Thresholds: University Interscholastic League (UIL) WBGT activity guidelines, as adopted by this project. WBGT figures are estimates derived from National Weather Service data, not on-site instrument readings.