County Has New Heat Tool

The Multnomah County Health Department has a new tool to better respond to extreme heat: the Heat Vulnerability Index (HVI). Extreme heat events are becoming more severe in Multnomah County. They are happening more often, lasting longer and growing in intensity. The resulting risk of heat-related illness and death is a serious public health concern for county residents.

Since the June 2021 heatwave when temperatures reached 116 degrees, the County has been working to develop strategies to better identify the people at greatest risk, keep people safe in their homes and develop a collaborative system with other agencies and community-based organizations to focus on outreach and response. The HVI builds on similar tools to help the community prioritize and guide extreme heat response and long-term planning, incorporating current literature on the health impacts of extreme heat and climate change.

“The last two summers have taught us just how dangerous heat is. Now is a good time to make a plan to stay cool,” said Brendon Haggerty, Healthy Homes & Communities manager. “I hope the HVI is helpful for all the responding agencies for heat-related emergencies.” The HVI assesses heat vulnerability at the population-level, using three key factors: sensitivity to heat and illness; exposure to extreme heat and the elements of our built environments which regulate temperature; and the capacity to adapt to extreme heat and lessen harm.

The interactive tool displays how heat vulnerability, sensitivity, exposure and adaptive capacity differ throughout Multnomah County. The tool also includes the 19 indicators used to build the index. By making this tool available to the public, it can be used to help health and service organizations make long-term investments to reduce heat impacts and short-term response plans during heat events.

“Our Environmental Health team has done some great work with the improved HVI tool and I know it will help us tackle these big challenges in an even more data-driven fashion,” said Valdez Bravo, Health Department interim director. “These are really great tools to have as part of our decision-making and strategies.”

The HVI will allow the county, cities, partner agencies and community-based organizations, including culturally specific and culturally responsive organizations, to make coordinated, geographically-targeted outreach efforts to help keep people most at risk safe in their homes. It can also help prioritize outreach to houseless individuals.

“Heat can kill people outdoors and in their own homes. Tragically we learned that in the last few years,” said Jessica Guernsey, Public Health Division director. “This tool will help save lives and is an example of core public health work in Multnomah County.”

The HVI, which can be accessed at, displays our area in map form with heat vulnerability percentiles indicated by colored blocks. Filters can be applied to determine “sensitivity”–for example, the percentage of the population that are greater than 65 years old living alone. “Exposure” looks at factors like tree canopy and housing density while “adaptive capacity” displays percentages of the population in rental housing, English language proficiency and more.

When temperatures rise, there are two other tools that individuals can access to find relief from the heat. Help for When it’s Hot tool ( includes information about identifying symptoms of heat illness, caring for yourself and others during hot weather and more. 

There is also an interactive map, at, that shows where to find indoor cool spaces (including libraries and community centers) and outdoor cool spaces (including splash pads, misting stations and water filling stations).

County Has New Heat Tool

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