A line of severe thunderstorms rolled across Western Pennsylvania early Monday evening, spurring tens of thousands of power outages and exacerbating concerns over how residents can stay cool amid what’s forecast to be at least six consecutive days of temperatures in the mid- to upper 90s. Areas north of Pittsburgh appeared to be hardest hit. Tens of thousands of Duquesne Light customers around the region had lost power Monday evening. In a news release received at about 10:40 p.m., Duquesne Light said more than 48,000 customers were without power. More than 11,000 West Penn Power customers were without power as of about 11:50 p.m.