National Weather Service, CDC Unveil New ‘HeatRisk’ Forecast

3 min read

April 23, 2024 – The National Weather Service will now issue heat warnings in a new way using a system called HeatRisk. 

The weeklong forecasting system will help people make plans with heat safety in mind, and it will also help health care systems and other businesses affected by extreme heat to be prepared for workflow changes, such as adjusting staffing in emergency rooms and urgent care clinics, or adjusting schedules for outdoor workers.

The system was developed by the CDC and the National Oceanic and Atmospheric Administration, and it was unveiled Monday. Here’s how it works:

  • HeatRisk levels range from 0 to 4 and have color codes. The top two colors are red (for Level 3, or Major Risk), and magenta (for Level 4, or Extreme Risk).
  • The levels combine several factors beyond temperature, like a lack of overnight relief from heat or unseasonably high temps, both of which can affect your risk of getting heat-related illnesses and can worsen health conditions.
  • Each day will have a risk level, and forecasts are published for 7-day periods.

The CDC hosts a webpage where people can look up HeatRisk by entering a ZIP code. As with many weather forecasts, HeatRisk can be reported with a map view, where swaths of colors change as the days of the week unfold, showing at a national, regional, and local level where people may need to plan to stay safe due to heat dangers. 

For example, this week’s national HeatRisk map shows that midweek, southern Texas and the Houston area are expected to have a Level 2 HeatRisk. Level 2, which is orange, means there's a moderate risk, affecting most people who are sensitive to heat.

A Major (red) HeatRisk means all people will be affected if they don’t have access to cooling and hydration. An Extreme (magenta) HeatRisk is defined as “rare and/or long-duration extreme heat with little to no overnight relief” and is expected to have widespread community impacts. 

On the opposite end of the scale, low HeatRisk levels will be important alerts to help people who are heat-sensitive or their caretakers know that precautions are needed, such as planning for access to cooling and ensuring adequate hydration. Sensitive groups include children and adults with health conditions, pregnant women, and outdoor workers.

“As climate change intensifies, extreme heat events are becoming more frequent, more severe, and longer. Issuing alerts and health advisories before or during periods of extreme heat can save lives,” the HeatRisk website states.

Local HeatRisk levels won’t just take into account temperature, but also historical health data tracked by the CDC, such as how many local emergency room visits due to heat have been reported in the past. When HeatRisk developers combined their new risk levels with information in Arizona such as ER visits and heat-related calls to local fire and health departments, the highest risk levels corresponded with the days that had the most emergency calls or ER visits.

A new CDC report suggested that men and younger and middle-aged adults may need to take more precautions when temperatures climb. Men were more than twice as likely as women to visit ERs during 2023 to be treated for heat-related illnesses, and adults ages 18 to 64 years old were more likely than those ages 65 and older to be treated for heat-related health problems in ERs, too. Overall, heat-related illnesses treated in emergency rooms nationwide in 2023 surpassed rates recorded from 2018 to 2022.