ROME — Snow made a rare appearance in Rome on Monday, paralyzing the Italian capital for hours, hobbling the public transport system, and snarling air, road and rail transportation. The army was enlisted to help spread salt and to shovel slush from the city’s streets, where dozens of cars had become stranded.

With schools in the city closed for the day, and hundreds of shops shuttered, many Romans took the unexpected blanket of white in cheerful stride, taking to the streets to record the snowfall on social media and to wage boisterous snowball fights, including one in St. Peter’s Square in the Vatican.