In 2023, the United States experienced record-breaking heat waves, leading to a significant increase in emergency department (ED) visits for heat-related illness (HRI). The CDC analyzed data from the National Syndromic Surveillance Program (NSSP) to compare daily HRI ED visit rates during the warm-season months (May–September) of 2023 with those from 2018–2022. During 2023, daily HRI ED visit rates peaked in several regions and remained elevated for an extended period. More males than females sought care for HRI, especially those aged 18–64 years. The risk of HRI ED visits was highest during July and August, with rates more than three times higher than in other warm-season months. Regional differences were notable, with Region 6 reporting the highest rates. The findings highlight the need for public health interventions to address the increased risk of heat-related illness, particularly among vulnerable populations. The CDC issued public health alerts to raise awareness and guide prevention efforts. As climate change leads to more frequent and intense heat waves, monitoring heat-related health impacts is crucial for public health preparedness and response. The study underscores the importance of timely data collection and analysis to inform public health strategies and protect communities from the effects of extreme heat.In 2023, the United States experienced record-breaking heat waves, leading to a significant increase in emergency department (ED) visits for heat-related illness (HRI). The CDC analyzed data from the National Syndromic Surveillance Program (NSSP) to compare daily HRI ED visit rates during the warm-season months (May–September) of 2023 with those from 2018–2022. During 2023, daily HRI ED visit rates peaked in several regions and remained elevated for an extended period. More males than females sought care for HRI, especially those aged 18–64 years. The risk of HRI ED visits was highest during July and August, with rates more than three times higher than in other warm-season months. Regional differences were notable, with Region 6 reporting the highest rates. The findings highlight the need for public health interventions to address the increased risk of heat-related illness, particularly among vulnerable populations. The CDC issued public health alerts to raise awareness and guide prevention efforts. As climate change leads to more frequent and intense heat waves, monitoring heat-related health impacts is crucial for public health preparedness and response. The study underscores the importance of timely data collection and analysis to inform public health strategies and protect communities from the effects of extreme heat.