Climate and volcanic risk: Vesuvius and the Campi Flegrei

The climate

Naples has a typical Mediterranean climate: mild rainy winters (rainfall is concentrated between October and March), long hot humid summers with muggy nights in the city, pleasant shoulder seasons. Snow in the city is very rare. Air quality is a problem in traffic areas: among Italy's large cities Naples records one of the highest numbers of days above the daily PM10 limit (see data), because of traffic in a compact city with poor ventilation in its basins.

Campi Flegrei: bradyseism and alert level

West of the city lies the Campi Flegrei caldera, an active volcano that includes Pozzuoli, Bacoli and several western districts of Naples. Since 2005 a phase of ground uplift (bradyseism) accompanied by earthquakes has been under way; the alert level has been yellow since 2012 and seismicity has intensified since 2023, with events up to magnitude 4.6 and a cumulative uplift of more than 150 cm; a decree of 30 October 2025 declared the second-level "attention" operational phase, which strengthens monitoring and verifies the civil-protection measures already planned.

The Campi Flegrei red zone — the area where, in case of alarm, preventive evacuation is the only protective measure — includes the municipalities of Pozzuoli, Bacoli, Monte di Procida and Quarto, parts of Giugliano and Marano and, in Naples, the whole of Soccavo, Pianura, Bagnoli and Fuorigrotta, plus parts of San Ferdinando, Posillipo, Chiaia, Arenella, Vomero, Chiaiano and Montecalvario: about 500,000 inhabitants. The yellow zone (ash fall) covers 24 quarters of Naples and six municipalities, more than 800,000 people.

Vesuvius

Vesuvius has been dormant since the 1944 eruption, with only fumarolic activity and low seismicity: green alert level. The national emergency plan is based on the scenario of a sub-Plinian eruption like that of 1631 and defines a red zone of 25 municipalities in the provinces of Naples and Salerno, which in Naples partly includes the quarters of Barra, Ponticelli and San Giovanni a Teduccio, and a yellow zone of 63 municipalities and three Neapolitan circoscrizioni (the plan's term) exposed to ash fall.