Near real-time heat-related illness data

Extreme heat is dangerous. It can cause heat-related illness, make chronic conditions worse, and even kill. The weather forecast is our best way to predict heat-related health outcomes. We can also track heat-related illness with near real-time electronic data from emergency departments at hospitals throughout NYC.

This is called syndromic surveillance, and it helps us track citywide trends. Typically, 10,000 people visit an emergency department (or ED, also called the emergency room) every day in NYC. When somebody visits the ED, they're examined, and asked to describe how they feel. These findings are recorded, and hospitals send these records to the Health Department. We search these records for diagnostic codes (when available) and words describing why patients are at the ED to track specific health conditions in near real-time.

Below are data on the number of heat syndrome visits to emergency departments, and the daily maximum temperature. What do we use these data for?


In NYC, an extreme heat event is two or more days with a heat index reaching 95 °F, or one or more days reaching 100 °F.

To learn more about heat and health, visit Extreme Heat and Health. To stay safe in the heat, visit Beat the Heat.

Annual data

Select a year to view data:                       
Max daily temperature is the heat index or temperature, whichever is higher, as recorded by the National Weather Service weather station at La Guardia Airport.

Data from 2017 to 2020