Content-Length: 50948 | pFad | https://www.weather.gov/safety/heat-index
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The National Weather Service (NWS) has multiple tools to assess the potential for heat stress due to extreme temperatures. The following tools can inform the issuance of NWS official heat watches, warnings, and advisories. Each of these tools integrate other weather parameters to provide a deeper level of information beyond what the actual air temperature can tell us. View the NWS Heat Tools reference sheet for more details.
The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature. To find the Heat Index temperature, look at the Heat Index Chart above or check our Heat Index Calculator. As an example, if the air temperature is 96°F and the relative humidity is 65%, the heat index--how hot it feels--is 121°F. The red area without numbers indicates extreme danger. The National Weather Service will initiate alert procedures when the Heat Index is expected to exceed 105°-110°F (depending on local climate) for at least 2 consecutive days.
NWS also offers a Heat Index chart for areas with high heat but low relative humidity. Since heat index values were devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15°F. Also, strong winds, particularly with very hot, dry air, can be extremely hazardous.
What is Wet Bulb Globe Temperature (WBGT)? Check out this handout and video to learn about WBGT.
WBGT uses temperature, humidity, wind, solar radiation, and other weather parameters. It’s a particularly effective indicator of heat stress for active populations such as outdoor workers and athletes.
WBGT can be used to inform activity modifications during exercise or outdoor work. For instance, The American College of Sports Medicine bases its guidelines for the intensity of sport practices on WBGT, and it is therefore utilized by athletic programs in many school districts.
The Occupational Safety and Health Administration (OSHA) recommends protective measures for outdoor work:
For more information:
Please Note: HeatRisk is an experimental product and is not supported 24/7. Changes may occur without advance notice.
The NWS HeatRisk forecast provides a color and numeric value that places forecast heat for a specific location into an appropriate level of heat concern, along with identifying groups potentially most at risk at that level. HeatRisk is accompanied by recommendations for heat protection and is a useful tool for planning for upcoming heat and its associated potential risk.
Based on the high resolution NWS national gridded forecast database, a daily HeatRisk value is calculated for each location from the current date through seven days in the future.
HeatRisk takes into consideration:
For more information
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