Summer in Northern China is hot and somewhat wet. May through August and high temperatures regularly top over 30 °C (86 °F), with lows rarely falling below 15 °C (59 °F). You will have no issue leaving warm clothing at home, though waterproofs might be useful as about 75 percent of the regions rain falls over this period and precipitation averages 100 mm in June.
It is for this season that the country's Central 'three furnace-like cities’ of Chongqing, Wuhan and Nanjing earn their name. In July and August the average highs are 33 °C (91 °F) for each city. Umbrellas are essential, though it is worth noting the rain comes in spits and spurts and is rarely constant.
With the arrival of the monsoon, Southern China becomes hot and wet. Precipitation hits about 145 mm per day in Nanning, capital of Guangxi Autonomous regions, and about 140 mm per day in Kunming in Yunnan Province in July. While average highs hit around 33 °C (91 °F) over the summer in Nanning, the higher elevation of Kunming (around 2,000 meters) make it significantly cooler with highs of just 24 °C (75 °F) and lows a warm 17 (63 °F).
Northwest China is warm with occasional rains, a good time to visit the small region of Ningxia, a sparse desert region lying on the Loess Plateau and the plains of the Yellow river, containing abandoned sections of China’s Great Wall. Yinchuan, the region’s capital, sees average highs of 31 °C (88) in June/July with precipitation averaging around 32 mm per month, with most days dry. Xining, capital of Qinghai, is something of a summer resort for the region, with highs around 24 °C (75 °F) and lows of around 10 (50). Precipitation reaches around 80 mm, making umbrellas useful on some days.