Overview
- The National Weather Service issued an extreme heat warning for the Philadelphia area on July 4, 2026, forecasting heat-index values of 105–110°F through the evening.
- Parade organizers canceled the Salute to Independence Semiquincentennial Parade after daytime temperatures hit triple digits and the city tied a 103°F reading the previous day.
- The NWS cautioned that very warm overnight lows in the mid-70s to low-80s would give no relief and that several near-record hot days would worsen heat-related illnesses.
- Thomas Jefferson’s contemporaneous thermometer logs record a much milder July 4, 1776 with temperatures around 68°F at dawn and about 76°F by early afternoon, a contrast widely cited in coverage.
- Long-term analyses show July has warmed in roughly 94% of 243 U.S. cities since 1970 by about 2.6°F on average, raising the chance that El Niño-amplified heat waves will disrupt public events and increase risks for older adults, young children, low-income communities, and outdoor workers.