Weather tracker: More than 900 wildfires rage across Canada

Recent hot, dry weather in Canada has triggered hundreds of wildfires across the country. As of Wednesday, more than 900 were burning, scorching about 3m hectares of land. While fires have broken out in several provinces, the greatest concern is in the Northwest Territories and Ontario, where several remain out of control.Poor air quality has been reported across affected regions, with wildfire smoke carried by winds into the US and even across the Atlantic to northern Europe. The risk of further blazes remains high as North America enters the peak of fire season.Meanwhile, the city of Salta in Argentina recorded its warmest-ever overnight minimum temperature on Saturday, with the mercury failing to fall below 26C (79F). This reading is particularly remarkable because Argentina is in the middle of winter, when Salta’s average night-time minimum is about 3C.The previous warmest night at this weather station was 22.2C, recorded in January 1953 during the height of summer. This exceptional warmth was driven by the Zonda wind, which develops when westerly airflow crosses the Andes before descending, warming and drying as it sinks back to ground level.This process is known as the Foehn effect, a phenomenon that occurs on the downwind side of mountain ranges around the world. However, the intensity experienced in Salta last weekend was unusual. One contributing factor may have been the rapidly developing El Niño in the eastern Pacific, which would have left the incoming air mass warmer than average, even before it descended on the city.Elsewhere, the strengthening El Niño is also expected to increase typhoon activity in the western Pacific. Tropical Depression 11 formed on Tuesday before developing into Tropical Storm Noul north of the Philippines on Thursday night. The system is forecast to intensify into a typhoon over the coming days as it tracks between the Philippines and Taiwan, before making landfall on China’s south-east coast on Sunday morning local time as a category 1 storm.