Jinan has a typical northern Chinese continental climate: very hot and humid summers (July averages 27°C but feels hotter with the humidity), very cold winters (January averages -1°C), and pleasant but short springs and autumns. Spring — April and May — is the best time: the willows are in new leaf around the springs, temperatures are comfortable, and the spring flow is often at its highest after winter snowmelt. Autumn — October and early November — is the second-best option, with cool clear days and the foliage of Qianfo Mountain turning color.
Summer visits are viable but hot and sweaty; the lotus flowers on Daming Lake bloom in July and August and are worth seeing. Winter can be cold but the springs are at their most dramatic when steam rises from the heated groundwater into cold air, and the parks are nearly empty. The Confucius Birthday Festival in Qufu — mid-September — is worth timing a trip around if you plan to visit that area; the September atmosphere in Jinan itself is good for walking.