Emergency Preparedness and Response

Extreme Heat

As our climate changes, extreme weather events are increasing in both frequency and intensity. For many places, this means an increase in extremely hot temperatures. In addition to causing heat stroke, extreme heat conditions can exacerbate many health conditions, such as respiratory conditions, heart disease, diabetes, high blood pressure, and others. Extreme heat disproportionately affects low-income communities, who may lack the resources to pay for cooling in their homes, and communities of color, due to historic policies like redlining that forced these populations to live in worse-quality housing and neighborhoods that experience higher temperatures.

Keeping temperatures in the home thermally controlled is one of the 10 Principles of a Healthy Home recognized by the National Center for Healthy Housing because tenants and homeowners are at heightened risk for various health problems related to prolonged exposure to excessive heat or cold when their homes do not maintain adequate temperatures. Supporting the availability of resources, services, programs, and policies that improve thermal control in homes and ensure that homes are able to protect their residents during extreme heat conditions is a healthy homes issue.

Definition: The Centers for Disease Control and Prevention (CDC) define extreme heat as “summertime temperatures that are much hotter and/or humid than average” (Español). It is acknowledged that because average temperatures differ between locations, what qualifies as extreme heat in one place may not hold true for all locations.

Causes: As average local and global temperatures rise due to climate change, the threshold for extreme heat increases as well, resulting in more days of extreme heat and generally warmer temperatures. Climate Central’s Extreme Heat toolkit provides an animation explaining this shift and also includes other visual resources that show trends in rising temperatures.

Conditions that Worsen Heat

There are six factors that influence thermal comfort and how a person experiences heat; two are personal factors (clothing insulation and metabolic heat), while the other four are environmental and can therefore be controlled or mitigated in the home environment:

Air temperature. A NYC Health Department study, Protecting New Yorkers from Extreme Heat, found that 41 out of 48 people who died from heat stress in New York City between 2008 and 2011 had become ill from high indoor temperatures, and none of the 48 had a working air conditioner at home.

Humidity, which can prevent sweat evaporation and keep the body from effectively cooling itself. According to a report published by the National Oceanic and Atmospheric Administration (NOAA), occurrences of dangerously hot and humid conditions are occurring now –– decades before initially predicted.

Air velocity or air movement. Homes with little or no air movement can feel stuffy, and can also cause build up of pollutants in the air and expose residents to hazards. Ensuring adequate ventilation in a home is an important measure to control air movement. You can read more about ventilation, air movement, and heat in our Prepare and Act section.

Radiant temperature, which is the heat that comes from any warm object. Examples in the home can include radiators, ovens, stoves, and other appliances or household objects that produce heat.

Resource Library Table of Contents

Adverse Health Effects and Susceptible Populations
Two main health issues that can arise as a direct result of exposure to extreme heat are heat exhaustion and heat stroke. Extreme heat affects people differently depending on their age, occupation, health, and location. This section includes additional resources for each population group:

  • Those with chronic health conditions
  • Older adults
  • Young children
  • Outdoor workers
  • People experiencing homelessness

Prepare and Act
This section provides further resources on ways to prepare for extreme heat and what to do during the day.

Policy Levers and Actions 
For responses to extreme heat events to be effective, coordination and planning at the state and local level are important. The resources linked on this page offer resources and policy levers to help both mitigate heat impacts and reduce extreme heat events in the future.

Cooling Centers by State 
NCHH has compiled resources at the state level that include a comprehensive list of cooling center locations.


Latest page update: August 21, 2022.