New York Forecast Shows Heat Index Reaching 109 Degrees

Temperatures in New York are forecast to reach near 100 degrees Fahrenheit as the holiday weekend approaches. With added humidity, the heat index could climb to 109 degrees Fahrenheit. The National Weather Service has issued extreme heat warnings and watches across the Northeast. Cities from Detroit to Washington, DC, to Boston are also expected to see temperatures about 20 degrees above normal.

High humidity reduces the body's ability to cool through sweating. Richard Allan, a climate scientist at the University of Reading, said high humidity makes it much more difficult for the body to physiologically cool off. Overnight low temperatures are also expected to remain elevated.

The National Weather Service warned that several days of hot temperatures with little overnight relief can increase heat stress. New York mayor Zohran Mamdani posted that residents should develop a heat plan. The advice includes securing air conditioning access and checking on neighbors who may be vulnerable to heat-related illness.

The current heat wave follows record temperatures across Europe the previous week. Burning fossil fuels has made nearly every heat wave more intense than it would have been in a preindustrial climate, Allan said. El Niño conditions, declared earlier this month, are also contributing to higher temperatures across the northern United States.

The phenomenon is expected to strengthen through the summer.