It has been a weird few weeks of weather. In North America, Canadians and Floridians alike shivered through freezing temperatures, bomb cyclones and a polar vortex. (It got so cold that iguanas froze and fell out of trees.)Meanwhile, over in Australia, where it is summer now, it has been especially hot. Sweltering, really.In Sydney, temperatures hit 117 degrees Fahrenheit on Sunday, the hottest it has been since 1939. That oppressive heat, a side effect of climate change, has made life hard for the country’s humans and infrastructure. Heat waves result in 10 percent more calls for ambulances and 10 percent more deaths, local experts said. Police in Victoria, on Australia’s southeastern coast, warned drivers last week that a six-mile stretch of a freeway in the central part of the state had melted. A spokeswoman for VicRoads, which manages Victoria’s road systems, told the Australian Broadcasting Corp. that hot weather caused the asphalt to become “soft and sticky” and the road surface to bleed.