Resilient Fairfax Climate Projections

A foundational component of planning for climate adaptation and resilience is understanding the projected climate impacts for our area. In February 2022, the Resilient Fairfax team issued a comprehensive climate projections report which was supplemented by a report from the National Aeronautics and Space Administration (NASA) DEVELOP National Program entitled "Identifying Urban Heat Mitigation Strategies for Climate Adaptation Planning in Fairfax County, Virginia." Information on the findings of these two reports is available below.

Five images of various weather conditions

Climate Projections Overview

The Resilient Fairfax Climate Projections Report addresses two major questions: how has the climate changed? And, what will the future climate look like? The report digs into available data and climate models to help provide answers to questions like...

  • Will there be changes in temperature?
  • Will there be changes in storm severity?
  • Will there be changes in precipitation and intensity of rain events?
  • Will there be coastal flooding?
  • Will there be drought?
View Or Download The Full Climate Projections Report

Key Findings

  • Average annual temperature is projected to increase by as much as nine degrees Fahrenheit by 2085.
  • Average seasonal temperatures are projected to increase and warmer "summer" temperatures are projected to expand into the late spring and early fall months.
  • Extreme heat events are projected to increase. By 2050, Fairfax County could experience an additional month and a half of days above 90 degrees Fahrenheit per year.
  • By 2085, Fairfax County could experience up to 22 consecutive days at or above 95 degrees Fahrenheit per year.
  • The number of days below freezing per year is expected to decrease.
  • Currently, Fairfax County sees approximately 42 inches of precipitation per year. By 2085, the county is projected to see an additional three to four inches of precipitation per year.
  • More notably, the severity of precipitation events is projected to increase with fewer gentle precipitation events spread out over multiple days.
  • Precipitation is projected to increase across all seasons and future scenarios with a greater amount of rainfall expected during the spring and summer months.
  • While Fairfax County is not at high risk of drought, when meteorological drought conditions do occur in the future, the droughts may be amplified due to projected rising temperatures.
  • Scientific consensus suggests that though there may be a reduction in overall storm frequency in the Atlantic basin, there will be an increase in the intensity of the storms that do occur.
  • In one scenario, tropical cyclone wind intensity is projected to increase by five percent and precipitation rates are projected to increase by 14 percent.
  • Overall, there is a projected increase in the frequency of severe thunderstorms.
  • Fairfax County may see a possible reduction in snow days, shifting to an increase in rain days as temperatures warm.

The urban heat island effect creates temperature hot spots in areas with dense buildings and dark-colored surfaces such as asphalt. As part of the 2021 Summer National Aeronautics and Space Administration (NASA) DEVELOP project "Identifying Urban Heat Mitigation Strategies for Climate Adaptation Planning in Fairfax County, Virginia," NASA DEVELOP provided data and maps to show which areas in Fairfax County experience hotter temperatures than other areas in the county. The study found that:

  • The hottest spots in the county were in densely urbanized areas, with land surface temperatures as much as 47 degrees Fahrenheit above land surface temperatures in undeveloped forest reference areas.
  • The NASA DEVELOP team determined that areas within the county with higher tree canopy cover had greater heat mitigation capacity.
  • Urbanized areas of the county experience significantly hotter daytime temperatures compared to less urbanized areas.
  • Urban heat islands in the county include areas such as Tysons, Annandale, Chantilly, Centreville, Springfield, and Herndon.
View Or Download The Full NASA DEVELOP Report

Behind The Scenes: Report Methodology

Developing a full-scale climate projections report is a big undertaking. Estimating current and future conditions for Fairfax County required information from many sources and the use of several sophisticated analytical tools. Here are some of the most important elements of the report methodology.

  • Two types of climate conditions were considered for this report: chronic hazards that demonstrate historic and future trends (sea level rise, for example) and acute hazards, or events that may increase or decrease over time (severe storms, for instance)
  • The analyses generally used 30-year planning horizons. Time periods shorter than 20 years are not considered representative of climate change. The 30-year horizon was chosen to provide a more robust analysis of heavy precipitation and extreme heat events.
  • The report compares future projections to a baseline period (data from 1976-2005) and a current period (data from 1991-2020).
  • The projections primarily focus on a mid-century timeframe (2035-2064) centered  at the year 2050, and an end-of-century time period (2070-2099) centered at the year 2085.
  • To investigate future changes in climate, models were used to simulate a range of climate futures that represent, in part, how global society may evolve over the coming century.
  • For this report, two scenarios developed by the Intergovernmental Panel on Climate Change were used. The first assumes a continued increase in greenhouse gas emissions until 2040 and then a decline, with stabilization achieved by the end of the century. The second assumes significant increases in emissions through the end of the century. This scenario aligns with our current trajectory.
  • The analyses written up in the report relied on publicly available statistically downscaled climate model data developed by the Scripps Institute of Oceanography at the University of California, San Diego.
  • The projections also draw on data from three observation stations: Washington Reagan National Airport, Washington Dulles International Airport, and Vienna, Virginia.

For more information on the report methodology, please see page 10 of the full report.

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