Temperature Hazard Dashboard

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About Wet Bulb Globe Temperature (WBGT)

What is WBGT? The WetBulb Globe Temperature (WBGT) is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover (solar radiation). This differs from the heat index, which takes into consideration temperature and humidity and is calculated for shady areas.

WBGT vs. Heat Illness: The WBGT is used to manage heat stress and determine safe work/rest intervals in direct sunlight. High WBGT levels indicate that the body's ability to cool itself through sweating is severely compromised, rapidly increasing the risk of heat exhaustion and heat stroke.

UIL Recommendations (Class 3)

Organizations like the UIL mandate specific work-to-rest ratios and hydration breaks based on these categories. The threat scale varies by geographic region (climatology). The Houston/Galveston region falls into Class 3.

Military & OSHA Recommendations

The Military and OSHA utilize a uniform 5-category scale (Categories 1 through 5) for strict work/rest cycles and hydration requirements, specifically tuned for individuals performing moderate-to-hard physical labor in hot weather.

About NWS HeatRisk

What is NWS HeatRisk? NWS HeatRisk is an experimental color-numeric-based index that provides a forecast of the potential for heat-related impacts over a 24-hour period. Unlike heat index, it incorporates local climatology (what is unusually hot for your specific location), the duration of the heat (including lack of overnight relief), and CDC data on heat-health impacts.

Understanding the HeatRisk Categories

Category	Meaning
0 - Green Little/No Risk	Little or no risk from expected heat.
1 - Yellow Minor Risk	This level of heat affects primarily those individuals extremely sensitive to heat, especially when outdoors without effective cooling and/or adequate hydration.
2 - Orange Moderate Risk	This level of heat affects most individuals sensitive to heat, especially those without effective cooling and/or adequate hydration. Impacts possible in some health systems and in heat-sensitive industries.
3 - Red Major Risk	This level of heat affects anyone without effective cooling and/or adequate hydration. Impacts likely in some health systems, in heat-sensitive industries and infrastructure.
4 - Magenta Extreme Risk	This level of rare and/or long-duration extreme heat with little to no overnight relief affects anyone without effective cooling and/or adequate hydration. Impacts likely in most health systems, in heat-sensitive industries and infrastructure.

About the Heat Index

What is the Heat Index? Also known as the apparent temperature, the heat index is what the temperature feels like to the human body when relative humidity is combined with the air temperature.

The Role of Humidity: Evaporation is a cooling process. When you sweat, the evaporation of that moisture cools your body. When the relative humidity is high, the rate of evaporation decreases, meaning your body cannot regulate its temperature as efficiently, making it feel warmer. Conversely, in arid conditions with low humidity, perspiration evaporates rapidly, making it feel cooler than the actual air temperature.

Shade vs. Sun: It is important to note that heat index values are calculated for shady locations. If you are exposed to direct sunlight, the heat index value can increase by up to 15°F.

Heat Index Danger Classifications

Classification	Heat Index	Effect on the Body
Caution	80°F - 90°F	Fatigue possible with prolonged exposure and/or physical activity.
Extreme Caution	90°F - 103°F	Heat stroke, heat cramps, or heat exhaustion possible with prolonged exposure and/or physical activity.
Danger	103°F - 124°F	Heat cramps or heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity.
Extreme Danger	125°F or higher	Heat stroke highly likely.

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WBGT Temperature Heat Index Wind Chill HeatRisk

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Note: This is an experimental dashboard. Please report issues to jimmy.fowler@noaa.gov.

To use the dashboard:

- Toggle between different temperature parameters (WBGT, Temperature, Heat Index, and HeatRisk)

- You can learn more about WBGT, Heat Index, and HeatRisk by selecting the "i" button in the lower left of the map.

- Change map mode between today's max value, hourly forecast for today, or max forecast for the next 5 days. You can hide this window by clicking on Map Controls and Legend.

- Select a location to populate the time series (note: you can add a custom location by clicking on the map and giving that location a name).

- Making the dashboard full screen (using the expand button on the upper-right of the dashboard) is encouraged.

Houston/Galveston NWS Hazard Dashboard

Forecast Map

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