Deep-dive

Climate: fog, muggy heat and Po-valley air

Continental Po-valley climate: cold winters with fog and stagnant air, very hot and humid summers. PM10 exceeds the daily limit more often than in coastal cities; from October to March the regional anti-smog measures of ARPAE and the Region apply.

Sections: Seasons · Rainfall · Temperatures · Air quality · Environmental hazards

Seasons

Bologna sits on the southern edge of the Po valley at the foot of the Apennines: winter brings thick fog, especially in the flat northern areas (Bolognina, Corticella, the fair district) and night frosts, with occasional snow; the hills to the south are often above the fog. Summer is hot and muggy, with heat waves lasting weeks and nights above 20 degrees: the municipality activates plans for the elderly and the porticoes are the daily refuge. Spring and autumn are short and pleasant; rainfall is spread through the year, heaviest in autumn.

Air quality and anti-smog measures

The stagnant air of the plain concentrates fine particles: days exceeding the daily PM10 limit are more numerous than in coastal cities, though fewer than ten years ago. From 1 October to 31 March the anti-smog measures of the regional Air Plan (PAIR) apply, with restrictions on the most polluting vehicles in the built-up area from Monday to Friday, car-free Sundays and additional emergency measures when ARPAE forecasts exceedances on several consecutive days. ARPAE publishes the "Liberiamo l'aria" bulletin and air-quality forecasts; anyone arriving with an older diesel or petrol car should check whether it may be driven.

Hazards

The main natural hazard is extreme summer heat; the Emilia-Romagna floods of 2023 and 2024 mainly affected Romagna and the metropolitan area along the Savena, Idice and Ravone streams, with flooding in some parts of the city. The regional civil protection publishes colour-coded alerts.

Average temperature, January

City figurePeriod: 1991–2020Validsample unknown

Source: ISPRA – Valori climatici normali in Italia (web app SCIA, Sezione Climatologia Operativa), trentennio 1991–2020 · Serie urbana di Bologna (44 m s.l.m.).

4.7 °C

Average temperature, July

City figurePeriod: 1991–2020Validsample unknown

Source: ISPRA – Valori climatici normali in Italia (web app SCIA, Sezione Climatologia Operativa), trentennio 1991–2020 · Serie urbana di Bologna (44 m s.l.m.).

25.6 °C

Rainy days per year

City figurePeriod: 1991–2020Validsample unknown

Source: ISPRA – Valori climatici normali in Italia (web app SCIA, Sezione Climatologia Operativa), trentennio 1991–2020 · Stazione urbana dell'Ufficio idrografico di Bologna.

77days

Days per year above the PM10 limit (50 µg/m³)

City figurePeriod: 2024Validsample unknown

Source: SNPA – La qualità dell'aria in Italia nel 2024: PM10, tabella ISQA per stazione (dati ARPA/APPA, provvisori) · Dati 2024 elaborati dalle ARPA/APPA a fine anno, provvisori: le relazioni regionali definitive possono dedurre i superamenti attribuibili a polveri desertiche. Valore limite: max 35 giorni/anno. Altre stazioni: Giardini Margherita (urbana fondo) 15, Via Chiarini (suburbana fondo) 14 giorni.

26days