This summer’s sweltering sauna is inflicting much discomfort around the region as heat indexes frequently exceed 100 degrees Fahrenheit. On July 8, CNN headlined, “Persistent Heat Wave in the US Shatters New Records.” 

Heat-related illnesses have risen in the region. 

“Fairfax County has had the highest number of illnesses this season,” reported WUSA on June 27. On July 8, the county activated its emergency heat plan offering tips and cooling assistance. 

Heat Islands

Areas with hard surfaces and structures and few mature trees can be one to seven degrees Fahrenheit hotter during the day and one to five degrees warmer at night than “greener” areas, a phenomenon called “the heat island effect.” EPA explains: “Structures such as buildings, roads and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies. … pavements or roofing tend to reflect less solar energy and absorb and emit more of the sun’s heat compared to trees, vegetation and other natural surfaces. … Human activities like vehicles, air conditioning and industrial operations also emit heat into the urban environment.”

A Warmer Fairfax County     

“The climate in Fairfax County is becoming warmer, wetter and weirder,” says Matthew Meyers, Division Manager, Office of Environmental and Energy Coordination. “Extreme heat, flooding, severe storms and other changing hazards repeatedly impact our neighborhoods, infrastructure, services and natural resources.” The county’s 2022 Climate Adaptation and Resilience Plan says, “Fairfax County, Virginia is already feeling the effects of climate change, including more severe storms, increased flooding and amplified extreme heat.” And the plan predicts more frequent heat waves, among other impacts.

Northern Virginia’s ever-metastasizing expanse of development, roads, parking lots, roofs and other surfaces increase land surface temperatures in some areas. The Northern Virginia Regional Commission has mapped the heat island effect in Northern Virginia at https://www.novaregion.org/1509/Urban-Heat-Islands. It shows, for example, the U.S. 1 area as a hot corridor.

Vulnerable People 

The county’s climate and vulnerability index shows that 12 percent of its 1.15 million people and 27 percent of “vulnerable populations” are at risk during extreme heat periods. Hot weather can exacerbate existing vulnerabilities and disproportionately impact vulnerable populations. The county’s study found, 

“The Fairfax County population in general is highly exposed to extreme heat. Both the general population and the vulnerable populations received the maximum exposure score of three.” 

On vulnerability, the analysis says, “Based on available information, the general population in Fairfax County is estimated to have a moderately high total vulnerability to extreme heat. The vulnerable populations are estimated to have very high total vulnerability to extreme heat.”

Some people cannot escape to air conditioned buildings, like people who work outside. On July 8, the Faith Alliance for Climate Solutions requested window air conditioners for some residents of the Harmony Place Mobile Home Park on U.S. 1

Trees Lower Temperatures 

Increasing tree canopy coverage “is one of the most effective heat mitigation strategies,” the resiliency report contends, but tree cover varies greatly. 

American Forests developed tree equity scores for 200,000 U.S. urban neighborhoods. They found that neighborhoods impacted by poverty and which have a high percentage of minority residents average several degrees hotter because of the absence of trees.

In a May 21, 2024, memo to the Board of Supervisors, County Executive Bryan J. Hill reported that the county’s tree canopy cover increased by three percent between 2012 and 2021, an overall increase from 52 to 55 percent, to 138,866 acres. The county’s goal is 60 percent tree canopy cover. Staff estimate that 18 percent of land is a “possible planting area” and 27 percent of the county an “unsuitable planting area.” 

Despite this increase, Hill’s memo acknowledges the assessment’s shortcomings: “Staff remain cognizant that changes in forest composition, loss of mature trees and increased abundance of invasive plants are not fully accounted for in the study,” adding, “The data set primarily measures the spatial extent of tree cover and is less effective in assessing qualitative aspects of the forest ecosystem.”

Fairfax County uses the vulnerability index to prioritize tree planting and other activities to reduce greenhouse gas emissions, notes Meyers. 

What Can Be Done

To address these challenges, county officials cite their goal of 60 percent tree canopy, tree planting, the resilience and climate plans, comprehensive plan and urban design guideline updates and the One Fairfax policy, a commitment by the county to consider equity in county programs, policies and services.

The Board of Supervisors has reduced parking requirements in certain areas and requires trees in some parking lots for both county and private projects.

Stewart Schwartz, Executive Director of the Coalition for Smarter Growth, has suggestions: “We recommend planting street trees and partnering with nonprofits and landlords to plant trees in apartment complexes.  

“A major contributor to heat is the acres of wide roads and large parking lots resulting from the car-dependent development pattern. We've pressed for an end to road widenings and for large arterial roads to be converted to tree-lined boulevards with dedicated busways and bikeways. In addition, the redevelopment of commercial strip malls and their large parking lots is an opportunity to remove hard surfaces, replacing them with tree lined streets, green roofs, and larger forested stream buffers in return for developers building taller buildings." 

Ann Bennett, the Sierra Club’s Great Falls Group Land Use Chair, recommends, “strategically reducing large areas of asphalt and concrete and enhancing them with tree cover; providing cooling shelters; ensuring easy access to water; and providing increased green, open space or mini-parks as a respite for residents and pets. Planners should prioritize investment in neighborhoods and commercial areas deficient in cooling protections for those who need it most.”

Information

Heat Islands in Northern Virginia, https://www.novaregion.org/1509/Urban-Heat-Islands 

Tree Equity, https://www.treeequityscore.org/map#10.72/38.9071/-76.8208 

Community-wide Energy and Climate Action Plan, https://www.fairfaxcounty.gov/environment-energy-coordination/cecap 

Climate Adaptation and Resilience Plan, https://www.fairfaxcounty.gov/environment-energy-coordination/resilient-fairfax