Extreme heat events (EHEs) are the number one cause of weather-related injuries and death in the United States (CDC, 2020).
During 2004-2018 there was an annual national average of 702 heat-related deaths (CDC, 2020).
Prolonged heat exposure can cause increased strain on the heart as the cardiovascular system tries to thermoregulate internal body temperature and can trigger a variety of heat stress conditions. These health effects can be most significant in young children, the elderly, and other vulnerable segments of the population, making them the most at risk from extreme heat. In addition, extreme heat can affect mental health and behavior, significantly impacting individuals with mental illness posing higher risks for poor physical and mental well-being (CDC, 2020).
Increased heat can significantly deteriorate air quality. High temperatures can often be associated with high-pressure systems that stagnate over geographical areas causing a heat-dome. During this effect, air pollutants such as ozone, particulate matter, nitrogen dioxide, and other gases can be trapped, degrading air quality in an area. When inhaled, some of these pollutants, particularly ground-level ozone and particulate matter 2.5, can cause inflammation in people’s airways, potentially causing severe respiratory issues. These respiratory incidences can, in turn, cause an increase in asthma-related emergency room visits and hospitalization and can impact the health and well-being of small children, elders, and immunocompromised people (AARC, 2021).
Extreme heat presents a significant economic burden in many households struggling to meet the affordability of air conditioning and cooling demands.
In the U.S., outdoor workers have up to thirty-five times more risk of dying from heat exposure the general public (UCS, 2021).
Depending on present and future emission reduction efforts, outdoor workers' earnings could be impacted by $39 to over $55 billion dollar loss by midcentury, affecting workers, employers, and the overall economy (UCS, 2021).
Climate and Health- Heat
Climate and health experts with the National Integrated Heat Health Information System (NIHHIS) have identified factors that positively or negatively influence how climate can affect human health (Figure 13). Health outcomes are affected by social and behavioral factors that influence vulnerability for individuals (right box), natural and built environment factors (left box), and climate change. Certain groups are at increased risk of heat-related illness and death including children, older adults, pregnant women, outdoor workers, emergency responders and athletes (NIHHIS). Identifying populations at increased risk offers a way to reduce exposure and vulnerability through adaptive actions. Actions can be as simple and immediate as increasing public awareness or involve more planning such as increasing tree canopy and reducing impervious surfaces.
East Central Florida Region Observed Temperatures
The maps below illustrate each of East Central Florida's counties' average annual temperatures, maximum annual temperatures, and minimum annual temperatures for the 1985-2020 recorded period. Maximum and minimum maps show consistent warming throughout the years since 1980, with temperatures above the long-term mean for most of the time.
The warming temperatures observed in recent years have been primarily due to minimum temperatures versus daytime temperatures. This pattern is similarly represented across Florida. This higher temperatures have resulted in a narrowing of diurnal temperature ranges. Minimum temperatures best reflect the overall rise in temperatures observed in recent years and decades.
Brevard County- Annual Average, Maximum, and Minimum Temperatures
Lake County- Annual Average, Maximum, and Minimum Temperatures
Marion County- Annual Average, Maximum, and Minimum Temperatures
Orange County- Annual Average, Maximum, and Minimum Temperatures
Osceola County- Annual Average, Maximum, and Minimum Temperatures
Seminole County- Annual Average, Maximum, and Minimum Temperatures
Sumter County- Annual Average, Maximum, and Minimum Temperatures
Volusia County- Annual Average, Maximum, and Minimum Temperatures
Source (all graphs): NOAA, 2022
Projected Change in Number of Warm Nights
The maps on the right show the historical and projected number of warm nights (nights with minimum temperatures above 75°F) per year in the Southeast U.S. The top far right map illustrates a low-action greenhouse gas emissions scenario- RPC 4.5, and the bottom far right represents a higher greenhouse gas emissions scenario- RCP8.5).
Historically, the East Central Florida region has seen 20 to 30 more nights of about 75°F per year on average. However, projections show that with an RCP 4.5 scenario, this could increase to as much as 50 or more nights for most places out to the middle of the century (between 2035-3065). Moreover, projections estimate that with an RCP 8.5 scenario, nighttime temperatures will stay above 75°F for the lowest temperature season for about 100 nights per year. These estimated temperatures can significantly impact the region's economy, environment, and people's health and well-being.
2041-2070 Compared to 1976-2005
Source: NCA4, 2018
Historical and Projected Heat Index By County
The tables below show the average historical and projected frequency of extreme heat days for the East Central Florida region by county. The heat index values referred to in the table represent a function of temperature and humidity - the "feels like" measure. The term "off the charts" means extremely high heat index temperatures above 135°F, which can be severely dangerous for people's health and well-being. The two middle projection columns illustrate an RCP 8.5 scenario (high greenhouse gas emissions), whereas the last column reflects a scenario with limited emissions and capped warming to 2°C. Each estimated value presented reflects the average number of days per year above the heat index threshold indicated.
Historically, the region has regularly seen heat indices above 90°F; these are expected to continue to increase with the greatest rise in heat indices with values of 100-105°F. Depending on future global greenhouse emissions, heat indices above 100°F could quadruple by the middle of the century and after.
Source: UCS Report, "Killer Heat in the United States." 2019