Extreme cold and snow have hit large parts of Europe, with freezing temperatures causing railroad tracks in Poland to crack and snow blanketing most of the Turkish city of Istanbul. Temperatures dropped to minus 28 degrees Celsius (minus 18 Fahrenheit) in some areas of Poland overnight, the coldest night in 11 years. Many trains were delayed on Monday after rail tracks at two Warsaw railway stations cracked. In Istanbul, traffic was brought to a halt by the layer of snow covering the city, with some cars stalled or skidding on the roads. The flurries were forecast to continue throughout the day. The Nordic region - where winter weather is the norm - also saw snow and subfreezing temperatures, with the coldest temperatures predictably recorded in the Arctic. Norway´s meteorological institute tweeted a tongue-in-cheek message on Monday, saying: "We encourage all knitting lovers to send woolen clothes to their friends in the north."