Climate risk data methodology

The maps and data analysis for this site are based on peer-reviewed data provided by the First Street Foundation, a nonprofit science, technology, and research group focused on making it easier for the public to understand and act on the challenges posed to people's safety, property and life from climate change.

Among the tools the scientists developed are property-level risk assessments for wind, wildfire, flood and heat over the next 30 years - or the length of a standard home mortgage loan.

The organization's methodology is public online and we've linked it below for each of the four risk areas, allowing you to explore the details of the scientific approach the organization takes to each of these problems. While this presentation focuses on broad categories of risk across local geographic areas, First Street Foundation's Risk Factor tool lets anyone look at each of these risks specific to their individual property here.

WILDFIRE

For wildfire, the First Street Foundation model says a property is at "major" risk if it is forecast to have a 6% to 14% percent chance of being directly damaged by wildfire at least once over 30 years. The model says "severe" risk means a property faces at least a 15% chance over that time period.

The foundation's fire risk model includes all forms of fuel: trees, other vegetation and even homes themselves. It incorporates spread patterns from more than 500 historic wildfires, but taking into account hotter and drier conditions expected from changing climate. The model simulates more than 100 million wildfires.

The details of First Street's wildfire danger model are publicly available for anyone to review here. While the maps we've published here focus on the share of properties in geographic areas that fall within broad categories like "major" and "severe" risk, the foundation makes it possible for anyone to look up their individual property here.

HEAT

For heat, the First Street Foundation says a property at "major" risk would be forecast to experience an average heat index in July of 89 to 95 degrees over the next 30 years. A property at "severe" risk is forecast to endure an average July heat index above 95 degrees.

The foundation's Heat Factor model considers a wide range of factors, including high-resolution measures of land surface temperatures from satellites, proximity to water, ground and tree cover and humidity, among other measures. Adjustments are made based on forecast pollution scenarios. The heat model determines how many days a person at a property could expect to experience dangerous heat.

The details of First Street's heat model are publicly available for anyone to review here. While the maps we've published here focus on the share of properties in geographic areas that fall within broad categories like "major" and "severe" risk, the foundation makes it possible for anyone to look up their individual property here.

FLOODING

For flooding, a property faces a major risk when there is an 80% percent chance of it flooding at least once over 30 years, according to First Street Foundation's Flood Factor model. Severe risk means there is at least a 99% chance of the property flooding at least once over 30 years. But that's a rough approximation of a complex model. An individual property's Flood Factor risk score increases with higher probabilities of flooding or if flood water is forecast to be deeper.

The First Street Foundation's computer modeling considers far more factors than most government flood risk assessments, which focus primarily on historic flooding. First Street's models incorporate historic flooding, intense rainfall, rising seas, tropical storm surge, characteristics of buildings and the forecast influence of the warming planet.

The details of the organization's model are publicly available for anyone to review here. While the maps we've published here focus on the share of properties in geographic areas that fall within broad categories like "major" and "severe" risk, the foundation makes it possible for anyone to look up their individual property here.

WIND

For wind from tropical storms and hurricanes, the First Street Foundation's model says a property at "major" risk has an 26% percent chance of experiencing tropical storm winds at least once over 30 years. For "severe" risk, a property has at least an 80% chance.

The computerized analysis uses tens of thousands of model storm tracks, considering local conditions such as roughness of land surrounding a property, to calculate the likelihood now and 30 years from now of wind storm damage.

Complete details of First Street's peer-reviewed wind model are available for anyone to review here. While the maps we've published here focus on the share of properties in geographic areas that fall within broad categories like "major" and "severe" risk, the foundation makes it possible for anyone to look up their individual property here.