Extreme Heat Dashboard

This dashboard, developed by the North Carolina State Climate Office and supported by the USDA Southeast Climate Hub, includes information and resources to help understand and track extreme heat and its impacts.

Heat Overview ☀️ Real-Time Data ☀️ Forecast Tools ☀️ Key Thresholds ☀️ Health Impacts ☀️ Future Projections

Heat Overview

With a complex phenomenon such as heat risk, boiling it down to a single number is challenging. After all, it depends on multiple environmental factors such as the exposure to temperature, humidity, and wind, as well as biological ones, such as how the human body perceives and responds to those hot conditions.

Most commonly, heat risk is measured and communicated using one of these three metrics:

• Air temperature is widely understood and measured, but it only captures one of the atmospheric factors that can produce heat stress.
• Heat Index also includes the effects of moisture via the relative humidity, but because it uses temperature measured in the shade, it does not reflect the level of heat experienced in direct sunlight.
• Wet Bulb Globe Temperature (WBGT) uses the most comprehensive approach, factoring in the air temperature, relative humidity, winds, cloud cover, and sun angle – all of which affect how the human body perceives and responds to heat. The calculation also includes the black globe temperature, measured in direct sunlight.

While it may not be as familiar to the general public, WBGT is the most comprehensive of these metrics and has significant advantages for assessing heat risk. After its original development by the US military, it is now used by organizations such as the NC High School Athletic Association to implement rest breaks and other safety measures for student athletes practicing outdoors.

Interpreting WBGT values can be a challenge since they tend to be lower than air temperature or Heat Index readings, and thus may not seem as severe. By using color-coded categories or threat levels, it’s much easier to tell what sort of risk – ranging from Low to Extreme – a given WBGT reading implies.

In North Carolina, the heat season is typically defined as running from May through September, but other parts of the Southeast region have a wider heat season, and extreme heat can occur outside of these bounds – as in March 2026, when areas like Fayetteville, NC, recorded their earliest 90-degree days on record.

Based on climatological maps from the Southeast Regional Climate Center, May and September tend to have fewer days at 85°F or greater – corresponding to the High and Extreme WBGT categories – while these hot conditions are quite common regionwide during the summer months of June, July, and August.

Real-Time Data

The best way to track heat conditions is through observations from weather stations in your area, and the gold standard are mesonet stations equipped with the special equipment – namely, a black globe thermometer – needed to calculate the Wet Bulb Globe Temperature.

The table below summarizes monitoring tools by state with various heat metrics available:

Forecast Tools

Heat forecasts are relatively easy to find; they’re available from many sources, including most smartphone weather apps. This curated collection of forecast tools includes some developed by our office, our partners, and the National Weather Service:

NWS Graphical Forecasts

Regional forecasts of hourly air temperature, apparent temperature (Heat Index or Wind Chill), and WBGT

Southeast Heat Monitor

Three-day WBGT forecasts with climatological context and heat health messaging; also see this tool’s documentation

SERCC Convergence Tool

Hourly WBGT forecast graphs highlighting times when various flag-level criteria are reached

NWS HeatRisk

Forecasts of the category-based HeatRisk index, which reflects the intensity, seasonality, and local rarity of extreme heat

Key Thresholds

WBGT’s color-coded categories make it easy to understand when heat reaches dangerous levels, but because it’s not measured everywhere and isn’t widely understood yet, it may not be an option for everyone.

In those cases, the more traditional Heat Index metric can still provide heat health context by using thresholds that have been developed by researchers.

Together with the Duke University Nicholas Institute Heat Policy Innovation Hub, the North Carolina Department of Health and Human Services evaluated historical emergency department visits to create seasonal, region-specific thresholds across the state. These are captured by their Heat Health Alert System, which is free for users across North Carolina to sign up for.

Recent research (still in process) at the North Carolina State Climate Office used a different methodology but found similar numbers as DHHS, especially for the early and late season periods. By comparing historical daily maximum Heat Index with WBGT as measured by the NC ECONet, we identified the relationship between those metrics, which allowed us to develop metrics to translate between them.

In this analysis, we found that in low-elevation areas, a Heat Index of 98°F captures 100% of Extreme WBGT days and 78% of High WBGT days, but only 6% of Moderate days. In higher-elevation areas, a Heat Index of 88°F similarly captures all Extreme and High days, 80% of Moderate days, and only 6% of Elevated days.

More information about this research will be added here after it is peer-reviewed and published.

These thresholds may vary across the rest of the Southeast region. Contact your state health department to ask whether they’ve done similar analysis to determine key Heat Index thresholds.

Note that the National Weather Service issues Heat Advisories using a higher Heat Index threshold; for North Carolina, this is 105°F for at least two consecutive hours. Based on our research and the advice of heat health experts, adopting lower thresholds in your own monitoring may help you catch other potentially impactful days even when an advisory is not issued.

Days per year meeting Heat Advisory or Excessive Heat Warning criteria (top) and High or Extreme WBGT criteria (bottom) based on NC ECONet data between 2020 and 2024.

Health Impacts

Heat is the deadliest weather hazard in the United States, causing hundreds of fatalities per year. These impacts are also largely preventable by understanding and practicing heat safety.

First, heat doesn’t affect everyone equally. Certain people tend to be more vulnerable based on increased exposure, lack of consistent access to cooling, or underlying medical conditions. Groups at higher risk of heat illness include:

• Newborns, children, and the elderly
• People managing illness or pregnancy
• People taking certain medications
• Low income households
• Athletes, outdoor workers and indoor workers in hot environments
• People who haven’t had time to acclimatize yet

Once heat begins to affect the human body, it’s important to take immediate action to avoid exhaustion or heat stroke, which can be deadly. Look for the signs of heat illness and be prepared to act or assist others showing these symptoms by moving to cooler areas, loosening clothing, drinking water, and seeking medical attention or calling 911, if needed.

Future Projections

Because of climate change, temperatures are warming at all hours of the day. In the Southeast region, this is resulting in more frequent heat waves and a longer heat season. These changes, combined with disparate infrastructure, socioeconomic status, and health behaviors among our population, make already at-risk groups even more vulnerable.

Future projections show these climate trends continuing, including 20 or more additional extreme heat days (with maximum temperatures at or above 95°F) per year, on average, across much of the region by mid-century.

The North Carolina Climate Science Report noted that it’s likely that the number of hot and very hot days will increase in the future, and it’s very likely that summer heat index values will increase because of increases in humidity.

In addition to warming summer days, we have also seen an increase in the number of very warm nights (with minimum temperatures at or above 75F) since 2005, and this change is expected to accelerate in the future, with an additional 10 to 40 very warm nights per year by mid-century.

To explore these projections, the Climate Toolbox’s Future Climate Dashboard tool can provide an overview of the historical and future number of days with Heat Index values above 90°F, 100°F, and 105°F.