Massachusetts Department of Public Health seal Massachusetts Environmental Public Health Tracking

Heat Stress Hospitalization

  • -1 = Data not shown when case counts < 11. These small numbers are suppressed to protect privacy.
  • Unstable rates must be interpreted with caution. To see more detailed data with stability information, please use the Explore Maps & Tables link on this page.
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Siloutte of a person in front of the sun.

Heat stress is defined as a constellation of explicit effects of hot weather on the body. These effects include heat or sun stroke (hyperthermia), heat syncope/collapse, heat exhaustion, heat cramps, heat fatigue, heat edema, and other/unspecified clinical effects attributed to excessive heat exposure.

Physiologic mechanisms such as sweating and circulating blood closer to the skin’s surface enable the body to maintain an ideal core body temperature. When heat exposure exceeds the body’s capacity to cool itself, however, core body temperature will rise and heat stress will develop.

Did You Know?

The year 2022 was Earth’s 6th hottest year on record. The 10 warmest years on record have all occurred since 2010. The National Oceanic and Atmospheric Administration (NOAA) projects the year 2023 is likely to rank among the 5 warmest years on record.


Any individual, regardless of age, sex, or health status can develop heat stress if engaged in intense physical activity and/or exposed to environmental heat (and humidity). The very young, the elderly and those with chronic health conditions such as cardiovascular disease, diabetes, or obesity, are more susceptible to the effects of heat.

The relationship between extreme heat and increased daily morbidity and mortality is well established. Hospitalization rates for heat stress are just one potential indicator of the impact of a changing climate. Tracking these data can help document changes over time and place, monitor vulnerable populations, and evaluate the results of local climate-adaptation strategies.

Data on hospitalization visits are collected by the Massachusetts Center for Health Information and Analysis (CHIA) from all acute care hospitals and satellite emergency facilities in the state. CHIA collects information on all inpatient hospital admissions and emergency department (ED) visits.

Data Considerations

When reviewing and interpreting heat stress hospitalization data, it is important to take into consideration the following:

  • Hospitalization data, by definition, exclude discharges from specialty hospitals (e.g., psychiatric), long-term care facilities, and federal hospitals that are exempt from state reporting requirements.
  • Heat stress hospitalization data do not include individuals who do not receive medical care or who are not hospitalized, including those who die in emergency rooms, in nursing homes, or at home without being admitted to a hospital, and those treated in outpatient settings.
  • Transfers from one hospital to another may be included in the dataset as separate hospitalization events.
  • Emergency department data include all heat stress hospitalizations that originated in an ED, including those later admitted as inpatients. For this reason, there is overlap between the two datasets and many patients are included in both the inpatient and ED hospitalization data reported on this site. Heat stress counts and rates should, therefore, not be summed across the two measures of hospitalization.
  • Hospitalization data are validated through a process of automated editing and report verification. In addition, each record is subjected to a series of edits that check for duplicate records, accuracy, consistency, completeness, and conformity.
  • Numbers and rates may differ slightly from those reported on the national EPHT portal. These differences may be due to file updates, differences in calculation methods (such as grouping ages differently or rounding off numbers at different points in calculations), and updates or differences in population estimates.
  • Data will only be presented to the public if the confidentiality rules of MDPH and CHIA are met. These are rules requiring data aggregation and cell suppression to protect privacy.
  • Rates are based on the residential location of cases and not necessarily the location where incidents occur.

For additional information, please read the FAQ.

Available Data on Heat Stress Hospitalization

Use the Explore Maps & Tables link on this page to access the following measures for heat stress hospitalization in your community. The most current available data will be shown. Be sure to check the site periodically as new data are added each year.

To protect privacy, no information is shown that could identify an individual.

  • Annual Number of Hospitalizations / ED visits
  • Annual Crude Rate per 100,000 Population
  • Annual Age-Adjusted Rate per 100,000 Population
  • Explore data in Tables, Charts, and Maps
  • All of the measures above are available by community, county, and statewide
More About the Data
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