Genoa has a humid subtropical climate of rainfall, preventing it from being classified as solely oceanic or Mediterranean, with a special note for the Genoa low.
The average yearly temperature is around 19 °C (66 °F) during the day and 13 °C (55 °F) at night. In the coldest months: December, January and February, the average temperature is 12 °C (54 °F) during the day and 6 °C (43 °F) at night. In the warmest months – July and August – the average temperature is 27.5 °C (82 °F) during the day and 21 °C (70 °F) at night. The daily temperature range is limited, with an average range of about 6 °C (11 °F) between high and low temperatures. Genoa also sees significant moderation from the sea, in stark contrast to areas behind the Ligurian mountains such as Parma, where summers are hotter and winters are quite cold.
Annually, the average 2.9 of nights recorded temperatures of ≤0 °C (32 °F) (mainly in January). The coldest temperature ever recorded was −8 °C (18 °F) in February 2012; the highest temperature ever recorded during the day is 38.5 °C (101 °F) on the August 2015. Average annual number of days with temperatures of ≥30 °C (86 °F) is about 8, average four days in July and August.
Average annual temperature of the sea is 17.5 °C (64 °F), from 13 °C (55 °F) in the period January–March to 25 °C (77 °F) in August. In the period from June to October, the average sea temperature exceeds 19 °C (66 °F).
Genoa is also a windy city, especially during winter when northern winds often bring cool air from the Po Valley (usually accompanied by lower temperatures, high pressure and clear skies). Another typical wind blows from southeast, mostly as a consequence of Atlantic disturbances and storms, bringing humid and warmer air from the sea. Snowfall is sporadic, but does occur almost every year, albeit big amounts in the city centre are rare.
Annual average relative humidity is 68%, ranging from 63% in February to 73% in May.
Sunshine hours total above 2,200 per year, from an average 4 hours of sunshine duration per day in winter to average 9 hours in summer. This value is an average between the northern half of Europe and North Africa.