Playing conditions — whether it be heat, altitude or pitch quality — have been a big talking point through the World Cup. And there have been fears it could extend to Sunday’s final, in unprecedented circumstances.Spain and reigning champions Argentina meet in the summer tournament’s showpiece event at MetLife Stadium, New Jersey on Sunday. Kick off is set at 3pm ET/12pm PT/8pm BST.However, in the days leading up to the final, New York has been hit with poor air quality, as a result of wildfires in Canada which have sent acrid smoke sprawling across multiple major cities in the United States.Conditions improved significantly on Friday, but a White House official has indicated that informal discussions have taken place with FIFA and World Cup task force CEO Andrew Giuliani over the matter — so uncertainty remains.Here, The Athletic takes a look at the situation, and how it could affect the 104th, and very last, fixture of this summer’s World Cup.What has happened in Canada and how has this impacted New York and New Jersey?Polluted air has swept southwards, across the Northeast of the U.S. in recent days from wildfires in northern Ontario, Canada.The Canadian Interagency Forest Fire Centre (CIFFC) reported 897 active fires in the country on Friday, of which 31 were new. The majority of these were labelled by the CIFFC as being out of control.A heat dome — an area of high pressure in the atmosphere which has scorched North America — has pushed temperatures close to 100 degrees Fahrenheit in Ontario and the U.S. Northeast this week, while Thursday saw highs of 92F(33C) in New York City. A similar temperature is forecast Friday.This heat dome traps the smoke from faraway wildfires close to the ground, resulting in hot, humid, hazy, and ultimately unpleasant conditions.World Cup final weather forecast: Air quality alert caused by wildfire smoke, rain may help clearAaron Mentkowski and Madison EadesAs of Friday, New York City remained one of the most affected regions in the U.S., with Detroit, Washington D.C. and Chicago also carrying particularly poor air quality, according to IQAir, which provides live rankings of the air quality in cities worldwide.An expected change of weather over the weekend, with rain forecast, is projected to continue the improvement already seen and provide cleaner air for the World Cup final, but it remains difficult to predict.On Friday, New York City’s air quality index reading — the Environmental Protection Agency’s measure of how bad the air is, recorded on its AirNow website — was up at 188. A reading of 150 or higher is considered “unhealthy” for most people. Skies in the city have been orange, with the smell of smoke in the air.MetLife Stadium, the 82,500-capacity venue for Sunday’s World Cup final, is situated a few miles from Manhattan, New York City. However, the air quality reading in East Rutherford, where the stadium is situated, has been slightly lower than that in New York City, according to AirNow.