WARSAW, Poland (AP) — Extreme cold and snow have hit much of Europe, with freezing temperatures cracking railroad tracks in Poland 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 Monday after rail tracks at two Warsaw railway stations cracked. Warsaw authorities also urged people to stay indoors, as smog spiked from the burning of coal for heating. In Istanbul, traffic was brought to a halt by the layer of snow covering the city. The flurries were forecast to continue throughout the day.