Dangerous heat wave to grip US through July Fourth weekend

Dangerous heat settled over parts of the Mid-Atlantic and Central Indiana. The National Weather Service has extended heat headlines through Friday and warned that the most intense stretch will land Thursday, July 2, and Friday, July 3. In the Philadelphia/Mt Holly forecast area, high temperatures from Wednesday through Saturday could reach 95 to 105 degrees for most areas, with heat index values between 100 and 110 degrees.

Overnight lows may only fall into the mid 70s to low 80s, leaving little nighttime relief and giving bodies less time to cool down before the next day’s heat builds again.

Saturday, July 4, is still expected to be hot and humid, although showers and thunderstorms could lower the extreme heat risk in some places. A cold front on Sunday, July 5, may bring more widespread relief, but until then the worst exposure is likely to come during the afternoons and early evenings, when direct sun, pavement heat and humidity combine at the highest levels. Some cooling could follow by Sunday and Monday.

People at greatest risk include older adults, young children, people with chronic medical conditions, outdoor workers and anyone without reliable air conditioning. The Centers for Disease Control and Prevention says more than 700 people die from extreme heat every year in the United States, and hot days are linked to worse pregnancy and birth outcomes as well as more emergency department visits and hospitalizations. Warning signs of overheating include muscle cramping, heavy sweating, dizziness, headaches, weakness, nausea and shortness of breath.

The Weather Service’s HeatRisk tool gives each location a daily, color-coded risk value for the next seven days using weather, climate and CDC heat-health data. OSHA guidance calls for employers to provide water, rest and shade, along with cool water and access to electrolytes for workers exposed to heat.