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NWS Experimental HeatRisk Forecast Provides Different View of Possible Heat Threats | The Weather Channel
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Heat Safety & Prep

NWS Experimental HeatRisk Forecast Provides Different View of Possible Heat Threats

HeatRisk Forecast Example

At a Glance

  • The NWS HeatRisk forecast provides a look at upcoming heat threats over the next seven days.
  • It is a five-tier numeric and color scale that highlights what areas and groups are at risk.
  • It is currently available in the western U.S. but is expected to expand nationally in 2023.

A forecast tool from the National Weather Service is expected to help Americans better understand the threat posed by heat, and it's likely to be rolled out nationwide in the near future.

The HeatRisk forecast from the NWS is an experimental product that provides a risk level with both a color and numeric value for the next seven days. The levels are designed to better assess what actions, if any, a particular group and area should take.

This is important because extreme heat is responsible for more weather-related deaths in the United States in an average year than any other hazard.

The numeric scale goes from zero to four, with zero indicating no elevated risk and four meaning a very high risk for the entire population due to long-duration heat, with little to no relief overnight. The color scale starts at green (no elevated risk) and then transitions to yellow (low risk), orange (moderate risk), red (high risk) and magenta (very high risk).

HeatRisk Categories
(National Weather Service)

One of the big differences with the HeatRisk forecast is that it uses data to identify unusual heat for a particular day and location.

This method allows it to better account for acclimation and variation in climatology across the U.S., according to the NWS. It also requires a high-resolution gridded climatology to put the forecast into context. In addition, it incorporates heat-health data from the Centers for Disease Control and Prevention (CDC) into the thresholds.

The HeatRisk forecast uses many temperature and humidity observations, not just the heat index. The HeatRisk takes into consideration how far above average temperatures (highs and lows) will be; the time of year; how long the heat will last; and if there is an elevated risk for heat complications (supported by data from the CDC).

HeatRisk can also be used for any level of heat and not just extreme events.

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This example shows the detailed HeatRisk forecast for the San Diego area with much of the area under a moderate to high risk.

Heat warnings, watches and advisories remain the official heat products from the NWS, but the HeatRisk forecast is being used to influence and add value to those products. The HeatRisk forecast has been available in the western U.S. since 2014 but is expected to expand nationally in 2023.

Heat-Sensitive Groups and What Actions To Take

The different levels of HeatRisk highlight which groups may need to be prepared and take action. Certain groups are more sensitive to heat and may be impacted at lower thresholds.

Groups that may be more sensitive include the elderly and very young, as well as those on certain medications, who work outdoors, who don't have a reliable source of cooling and/or hydration, who are not acclimated to a warmer climate and those who are sensitive to poor air quality.

Heat-related illnesses are serious concerns for those vulnerable groups. The first signs of heat-related illnesses are increased sweating and muscle cramps. Other signs include confusion, dizziness, rash, nausea and fatigue. Over time, heat exhaustion can set in, and if not treated, heat stroke can develop.

The HeatRisk also includes suggestions on what actions can be taken to avoid health complications from the heat.

For example, an orange risk – level 2 – highlights that people who are part of a heat-sensitive group, are exposed to the sun and are active, or those without air conditioning during the day, have a moderate risk. The suggested actions for those groups are to reduce time in the sun between 10 a.m. and 4 p.m., stay hydrated and in a cool place during the heat of the day, perform outdoor activities during cooler times of the day and to open windows at night.

The CDC offers a few tips to stay safe during heat waves: stay in air conditioning; take frequent breaks; drink more water than usual; avoid using the stove or oven; take cool showers or baths; and wear lightweight, light-colored clothing.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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