New: HeatRisk Provides Best Assessment of Summer Heat Impact

WOAY-TV (Oak Hill, WV): HeatRisk is a color-based index that provides a thorough overview of the risk for heat-related impacts.

Chief Meteorologist Chad Merrill has the information:

This product is meant to provide hot weather guidance for folks, especially asthma sufferers, the elderly, very young children and athletes. Utility companies can use it as a guide to assess when the biggest strain on energy use will be this summer.

Here’s an example of how the heat risk assessment is done:

Let’s say we hit a cool patch of temperatures the week before Memorial Day and then warm into the 70s for the holiday weekend. With the turn of the calendar, we see a major heat ridge develop in the East.

We are forecasting a low temperature of 64 degrees and high temperature of 82 degrees locally for the first day in June. The record high for June 1 is 86 degrees, so a high of 82 degrees ranks in the top 95-percent of the warmest days for June 1. Since the record warmest minimum temperature is 67 degrees, a morning low of 64 degrees is in the top 95-percent of warmest minimum temperatures.

So, after coming off a pleasant weekend, we see this big heat surge with well-above average temperatures….with not much relief overnight. The risk assessment for our region would likely fall in the red category, which means this level of heat will impact our entire southern West Virginia population and hospitals are likely to see an influx of heat related illnesses.


The HeatRisk product is partnership between the weather service and Center for Disease Control and Prevention to better serve the public’s needs. The study leading to the product looked at the lowest temperature that triggered a heat death in every part of the country. This served as the baseline for the Yellow, or lowest heat related impact category. The magenta category is only used for a stretch of two or more days with record highs and near record warm overnight low temperatures.

It’s important to note the temperatures that trigger each heat risk level is different, based on heat related deaths in other cities. For instance, the lowest heat risk category in Washington, D.C. falls within the range of 73 and 91 degrees during the middle of July. In a colder climate, such as our region, 91 degrees would exceed record highs and be in the red or magenta category.

For those reasons, if you travel to Miami this summer, you would pay more attention to when the Orange heat risk is forecast and take extra precautions because you are not acclimated to such heat that Miami sees on a daily basis in June, July and August.


When we do jump into the doldrums of summer, a weather service study from the Pacific Northwest heat wave in late June 2021 indicated temperatures inside homes without air conditioning were the warmest between 9-11 p.m.

Most deaths in that heat wave occurred in unairconditioned homes. This brings to fruition the lag between the warmest time of the day outside and warmest inside your home. So, for those without air conditioning during those brutal, hot, code orange and red days may want to consider staying at a neighbor’s or friends house at night and going home during the day when the home is the coolest.

To examine the NWS HeatRisk for the next several days across the U.S., click here.


Chief Meteorologist identifies the days most likely to see code orange or red heat risk for our region:

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