WASHINGTON CROSSING, Pa. (AP) — Extreme weather conditions enveloped the U.S. Monday as the East Coast recovered from flooding, sizzling temperatures beset the West and several northern states contended with unsafe air quality from Canadian wildfires. In Pennsylvania, emergency crews are still searching for a missing 9-month-old boy and his 2-year-old sister, whose family car was swept away in a weekend deluge. Meanwhile, Death Valley in California is flirting with record-high temperatures that could reach a staggering 125 degrees Monday. And finally, the Environmental Protection Agency says extensive swaths of the northern United States are experiencing unhealthy air quality as smoke from Canada’s wildfires pushes the air quality index into the red zone.