New Yorkers were gripped by the worst urban air quality in the world Thursday, and Americans could face days or even weeks of smoky siege from the drifting haze of unrelenting Canadian wildfires.Hundreds of community parks, ballfields and other outdoor spaces from Canada to North Carolina sat empty as air quality readings in many areas ranged from unhealthy to hazardous. The low-pressure system adrift over Maine and Nova Scotia that has helped funnel the ashen air will probably be "hanging around at least for the next few days,” National Weather Service meteorologist Bryan Ramsey said.Conditions are likely to remain unhealthy until the wind direction changes or the fires are doused, he said.“Since the fires are raging, they’re really large, they’re probably going to continue for weeks," Ramsey said. "It’s really just going be all about the wind shift.”The good news, AccuWeather reports, is that parts of the Northeast could see modest air quality improvements through the day Thursday, a...