Canadian wildfires have sent smoke into the northeastern US. More than 700 fires are burning across Canada from the Arctic Circle to southern Ontario. Forest-fire smoke has drifted south triggering air-quality alerts in New York City and from Minnesota to Maine. The smoke from large wildfires raises health risks and has been blamed for hastening the melting of Arctic ice, since the soot absorbs more heat. In recent years, the plumes have drifted into US cities, most notably New York and San Francisco, turning skies orange and driving residents indoors to escape the irritants floating in the atmosphere.