Shanghai is located on the East China Sea midway between Beijing and Hong Kong. It sits on alluvial delta land near the mouth of the Yangzi River. Like huge river deltas around the world, the Yangzi Delta is a watery place. The many rivers, canals, streams and lakes make for abundant water but also for a climate that is quite humid year around.
According to Wikipedia Shanghai has a “humid subtropical climate”. There are four distinct seasons. Winters are long (November-March), chilly and damp. Cold northwesterly winds from Siberia make daytime temperatures, which rarely drop below freezing, feel much colder. Nighttime temperatures occasionally drop below freezing. But most years there are no more than one or two light snowfalls.
Summers (June-August) are hot and humid. While June is known as “the rainy season”, Shanghai is subject to freak thunderstorms, tropical storms, and typhoons which can dump prodigious amounts of rain in short periods. About 70% of the annual rainfall occurs between May and September.
The most pleasant seasons are spring, although changeable and often rainy (approximately April-May), and autumn, which is generally sunny and dry (approximately September-October).