This refers to yesterday's feast of St. Januarius (Gennaro in Italy). The miracles has something of an "appearance of the groundhog" lore attached to it, but it happened and that's supposed to be good for everyone.
From Agenzia Giornalistica Italia - News In English:
"At 9:57am, after less than one hour's praying, the miracle of the liquefaction of the blood of St.Gennaro, patron saint of Naples, occurred in the Cathedral, jam-packed with believers. The 'miracle' usually takes place three times a year: on the 19th September, the day of St.Gennaro, anniversary of his decapitation, which dates back to Diocletian's persecution; on the first Saturday of May, anniversary of the transfer of the saint's relics from Fuorigrotta (formerly Agro Marciano) to the catacombs; and on the 16th December, anniversary of a terrible eruption of Mt. Vesuvius in 1600. In the latter case, the miracle is rare. The 'miracle' is thought to bring good luck to the city and to the entire world. The liquefaction was announced by the believers in the church - following tradition - by the waving of a white handkerchief by the delegate of treasury. It was then time for fireworks and ringing bells."