With a humid subtropical climate, Shànghǎi is often grey and overcast, so don’t bank on the clear blue skies of winter Běijīng. With a mean temperature of around 18°C, Shànghǎi starts the year shivering in mid-winter, when temperatures can drop below freezing and vistas are grey and misty. The Shànghǎi cold is not the dry, biting cold of Běijīng, but a clammy chill that seeps into the bones. Few apartments have central heating in winter, and heating will come from air-con, if at all.
Spring brings warming days and lovely blossom to town, making March to mid-May probably one of the best times to visit weather-wise. As the weather warms, Shànghǎi residents take to wandering about town in pyjamas. Autumn (late September to mid-November) is also very pleasant, but it can still be very hot in September.
Summer may be the peak travel season, but the hot and humid weather makes conditions outside uncomfortable, with temperatures sometimes as high as 40°C (104°F) in July and August. The heat, a damp saunalike heat, is draining. June brings ‘plum rains’, saturating downpours that send pedestrians scrambling for cover as streets turn to rivers. Expect to see umbrellas in profusion on both wet and dry days as Shànghǎi girls shield their fair skin from the sun’s rays. Cooling winds blow into town in September and the temperature begins to slide, but watch out for sudden stingingly hot days at the tail end of summer, affectionately known as the Autumnal Tiger (qiūlǎohǔ). By December the thermal underwear is being unpacked. Rain is heaviest between June and September, but falls throughout the year.
In short, you’ll need silk long johns and down jackets for winter, an ice block for each armpit in summer and an umbrella wouldn’t go astray in either season.