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By Midcentury, Virginia Could See 30 Days Per Year With 100 Degree Heat Index

Heat Map of eastern united states
Analysis from Union of Concerned Scientists shows average days per year with a heat index above 100°F by Midcentury (2036–2065), if no action is taken on climate change. (Photo: Courtesy UCS)


new report from the Union of Concerned Scientists, a nonprofit science advocacy group, provides in-depth predictions for extreme heat this century.

The report refers to any day that exceeds a heat index of 90°F as “extreme heat days,” or days on which certain groups of people are more susceptible to harm when outdoors.

The Southeast is expected to experience the most extreme heat and the most drastic growth in extreme heat days nationwide.


Richmond Among Hottest Areas In Virginia

Virginia will be relatively better off than the Southeast as a whole, but that doesn’t mean things won’t warm up.

Astrid Caldas, a senior climate scientist with the Union of Concerned Scientists, says that Virginia historically sees about 30 days a year exceeding this threshold.  If no action is taken to combat climate change, however, that number will grow rapidly.

“These numbers would more than double to 75 by midcentury - by midcentury - that’s not by the end of the century, that’s like 30 years from now,” says Caldas.

Richmond, Williamsburg and Fredericksburg will experience extreme heat days more than any other Virginia cities.

Jeremy Hoffman, chief scientist at the Science Museum of Virginia, says that these days are often unbearable.

“Heat indexes that are above 100 degrees, like the ones that are predicted for this weekend, are so oppressive that any outdoor activity is severely limited or is recommended to be severely limited,” says Hoffman.

If no action is taken, it is predicted that Richmond will experience about a month’s worth of these days every year by midcentury.

Hoffman’s own research shows that different areas of the city heat at different rates.  This is due in part to differences in the surrounding architecture - areas with low-rising buildings and little green space heat the most.  These areas are often historically disenfranchised.

Rising heat could mean even worse conditions for people living and working in these areas.

“Off The Charts” Heat Will Affect More Americans Than Ever, Protective Measures Required

The study also accounts for heat indexes above 100°F and 105°F, both of which serve as thresholds for National Weather Service heat advisories, depending on where you are in the country.  But that’s not as hot as it gets.

As it turns out, the country will experience enough “off the charts” days -- days on which the heat index is literally unaccounted for by the NWS - to include them as their own category. 

Days like these, which pose serious health risks to all people and historically only occur in the absolute hottest places in America, threaten to become a reality in Southeast and Central U.S. by midcentury if no action is taken.  These days currently only reliably appear in America’s absolute hottest places.

This chart shows the limits of the NWS’s heat index measurement.  At the time of this system’s creation, any higher indexes were too infrequent to include. (Chart Courtesy of NWS)

The study calls for immediate action by all levels of government.  According to the researchers, drastically cutting back on carbon emissions is the priority.  

However, even if the actions taken meet the warming cap of 2°C put forth in the Paris Agreement, researchers say extreme heat days will still be more prevalent in the future than they are now.

They recommend a variety of measures that would protect those most susceptible to heat.  Among these is a request for Congress to provide heat-related directives to OSHA that would protect construction workers on extreme heat days.  

On the state level, the report encourages legislators to make new requirements for utilities that would ensure the power remains on during periods of extreme heat, even for those who can’t afford it.

The researchers also say that states and local governments need to develop plans for both heat adaptation and heat emergency responses.  Having some level of preparedness for these events could be a matter of life and death for some Americans, particularly vulnerable individuals.

States will likely have to address infrastructure problems.  Roads, railroads and electrical systems may not stand up to extreme heat, potentially hampering entire cities and towns.

Such measures aren’t designed to lower emissions or make any impact on climate change.  Rather, they would be put in place to create necessary protections for people against the rising temperatures that scientists are predicting for the future and the changes that we are already experiencing today.

This is story was reported by WCVE News Intern Patrick Larsen. 

Updated 5:30 p.m.


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