On July 4, 1911, record temperatures are set in the northeastern United States as a deadly heat wave hits the area that would go on to kill 380 people. In Nashua, New Hampshire, the mercury peaked at 106 degrees Fahrenheit. Other high-temperature records were set all over New England during an 11-day period.

The area from Pennsylvania northeast to Maine was most affected by the stifling heat. New York City was particularly hard hit. In fact, the New York City Health Department put out one of its very first heat advisories during July 1911. Mayor William Gaynor tried to make sure that the city’s ice dealers could keep up their deliveries; in the time before refrigeration, ice was critical in keeping the food supply from spoiling.

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By July 13, New York had reported 211 people dead from the excessive heat. One man, apparently disoriented from heat exhaustion, overdosed on strychnine. In Philadelphia, 159 people died from the heat. The types of deaths ascribed to the heat could vary quite a bit in 1911, with some authorities including in the count those who drowned while attempting to cool off by swimming. Heat also sometimes bent rail lines, causing train derailments; deaths in any resulting accidents might also be attributed to the heat. Heat stroke, however, is the typical cause of heat-related deaths. Extremely hot or humid weather or vigorous activity in the sun can lead the body’s temperature-regulation mechanisms to fail, causing body heat to rise to dangerous levels. Symptoms of heat stroke include a headache, dizziness, confusion and hot, dry, flushed skin, as well as a rapid heartbeat and hallucinations.

The end of the 1911 heat wave was marked by a severe thunderstorm that killed five people.