The 10-day heat index forecast for major competitive energy markets shows the same old sticky story in Texas. Chicago will cool off a bit, but Philadelphia and New York City are in ”extreme caution” each day. Boston will enjoy the only normal day over the ten-day period on July 29. Heat index utilizes temperature and humidity and is just one formula beyond temperature that can help determine cooling demand. Other formulas include the discomfort index, humidex, and wet bulb temperature.

For more:

https://www.weather.gov/ama/heatindex