Temperatures across China are forecast to plunge this weekend, as parts of the country reel from widespread disruptions caused by wintry conditions and heavy rains, including a subway collision in Beijing that left hundreds of commuters hospitalized. The cold snap comes after an abnormally warm fall, when the country logged its warmest October in decades. The average high temperature in the capital plummeted to about 15 degrees Fahrenheit (minus 9 degrees Celsius) on Saturday after hovering at around 50 degrees last week. Across China, meteorologists issued low temperature and strong…