China is a huge country, about the same size as the USA or Europe, with the greatest range of weather of any country on the planet. So, before you travel to China, it is recommended that you check the weather conditions. China is vast, and the climate and conditions vary widely from region to region.
Climates range from desert in Xinjiang (the Northwest), to Inner Mongolian grasslands, to temperate and alpine forests and farmlands, to rice paddies and sub-tropical vegetation, to tropical rainforest, to sunny beaches. There is the vast high-altitude plateau of Tibet and archipelagos of tropical islands.
Along with the seasons, latitude and altitude affect the temperature dramatically, with temperatures as low as -40°C in the north and as high as 40°C in the south. Distance from the monsoon rains of the tropics, generally defines the amount of rainfall in China, along with distance from the Pacific Ocean and the presence of mountains.
If a natural disaster occurs you should follow the advice of the local authorities. See China Travel Insurance.
The rainy season occurs between April and July in southern and eastern China (e.g. Guilin, Suzhou, and Hangzhou), from June until August in the north and west (e.g. Yunnan Province and Tibet), and between May and September for the areas near the Yangtze River (e.g. Chongqing and Yichang).
Rural areas near the Yangtze River and other rivers may be subject to flooding during their respective rainy seasons, and this may affect tourist activities on or near rivers.
Landslides are more likely to happen in southwestern China's mountainous areas, Yunnan and Sichuan provinces and Tibet, from May to September when the areas see plenty of rain. This may interrupt essential services and accessibility to tourist destinations, e.g. Longsheng.
Sichuan Province has experienced two sizable earthquakes in recent years. The 2013 quake caused some disruption to tourism around the Panda Research Base and Leshan, but no tourists were injured. Most recent quakes occurred in remote mountainous areas of West China with no effect on tourism.
Typhoons can occur during the wet season, usually from June to August, along the southern and eastern coasts. You should monitor weather reports if traveling in affected areas.
Beijing and Xi'an are dry, hot in summer and cold in winter. Shanghai (along with nearby Hangzhou, Suzhou and the Yellow Mountains), Guilin, and Hong Kong all experience monsoon rains in the spring and summer, with hot summers and milder winters.
Tourists visit Harbin in winter for its ice festival and ski slopes. Tibet has clear skies and big daily temperature differences and is best avoided in the frigid winter. The Silk Road in the Northwest is also best explored in the warmer months, when the deserts and barren vistas are at their best.
Tropical Hainan is a sunny escape for holidaymakers at any time of year. Chengdu is the overcast city, with muggy hot summers and cold dreary winters, and Kunming is the "Spring City" with pleasant mild weather all year round. For other tourist destinations see the list below.
North-Central China (Beijing, Xi’an) is similar in climate to Nebraska and Kansas, with less snow and rain during the winter. Dry with hot summers and cold winters, late winter and early spring bring regular dust storms and haze.
Southern and Central China (Shanghai, Guangzhou) is comparable to the Gulf Coast states, through winter storms do not occur as often. Rainfall is concentrated in the stormy monsoon months from late spring through summer, leaving autumn and winter relatively dry and settled. Summer is hot and humid. Winter is shorter, cool, and often overcast with drizzle.
Northeast China (Shenyang, Harbin) is similar to Minnesota. Dry with a short warm summer, and a long and very cold winter.
Xinjiang (Urumqi, Kashgar, etc.) experiences severe desert conditions with dramatic daily temperature swings. Summer can get very hot during the day, but generally cools off at night. Similarly, winter temperatures warm up during the day but plummet at night. In dramatic contrast to the desert are the snowcapped Heavenly Mountains, with their verdant pastures, near Urumqi.
Tibet (Lhasa, Shigatse, etc.) also sees marked daily temperature changes. When the sun shines (and Tibet is known for its blue skies), temperatures reach the mid 80s Fahrenheit (around 30°C) in the summer and the mid-60s (around 20°C) in the winter. At night or when it rains or snows, temperatures drop rapidly, maybe by 40 or 50°F (20 or 30°C). Precipitation is minimal in the winter; summer showers are more common, but occur mainly at night.
Choosing the best time to visit China depends on which places you wish to visit, and what type of weather you enjoy. May, September and October are the peak tourist months at China's most popular destinations when the weather is most comfortable, but prices are higher, and everywhere is more crowded.
Prices drop a bit in the shoulder season, which runs from late March through April and from June through August.
The low season arrives in late November, and continues through the winter when there are fewer crowds and the prices are lower. Also read: Why Travel in China's Winter Low Season?
The best time to see fall colors in China is from late October to early December, as parts of the country are saturated with fall hues.
Beijing's air pollution and traffic congestion are being tackled with improved public transport, restrictions on the use of vehicles, and the relocation of factories. Daily and localized variations in airborne particle levels are great, with some days below the WHO's strictest targets.
Beijing's air quality, apart from pollutants, is greatly affected by occasional dust storms, as is Xi'an's, in the spring, and humidity contributes greatly to the haze in summer, which is the worst time of the year for visibility and air quality. Shutterbugs will probably find an autumn trip best for photography.
Generally Beijing's pollution is not harmful, no more than an unpleasant smell or a mild throat irritant for healthy people. If you are sensitive to pollution you could buy pick up a 3M n95 mask in Beijing for 18 yuan. Breathing Beijing's air for six average days is the equivalent of smoking just one cigarette, which is not bad for a large developing world city.