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From north to south, China spans a range of latitude roughly equal to that between Mexico City and Lake Winnipeg in central Canada. Across this vast expanse of earth you can find climatic conditions as diverse as China's endlessly fascinating landscape. China is truly a land of climatic extremes. About 28% of the country, including Manchuria in northeastern China and the high elevations of the Tibetan Plateau and Tsinghai Province, are subarctic. Central and northern China, about 46% of the country that stretches from the deserts of Sinkiang Province across the North China Plain and south to Yunan and Hunan Province, are either cold-temperate, temperate, or warm-temperate. The remaining 26% of China, which includes the southern and southeastern coastal regions, is either subtropical or tropical. In short, China is a land of climate extremes.
Three of the world's great "weather engines" affect China's weather: the Siberian High, which generates northerly winds carrying dry, polar air into China; the Pacific High, which drives moist southwesterly monsoonal winds across East Asia; and the Indonesian Low, born of the warm waters of the western Pacific, it pushes vast amounts of moisture-laden air northward across the South China Sea. China's climate is characterized by monsoonal winds, with a northerly wind prevailing in winter and a southerly wind in summer.
China's warmest weather occurs in the southeastern subtropical provinces, where the summers are hot and humid. Average temperatures across this region range from 26 to 31°C (79 - 88°F). In general, temperatures decrease from south to north. Northeast China (Manchuria) experiences bitterly cold winters with temperatures dropping to as low as -37°C (-35°F). At the other extreme, in the Turfan Depression, known as China's "Oasis of Fire," summertime temperatures can reach a scorching 48.8°C (120°F).
The high altitude terrain of the Tibetan Plateau and neighboring Tsinghai Province is a special alpine cold zone where low temperatures are common all year round. The climate in Tibet sometimes behaves as if all four seasons have been compressed into one day. The temperature can be below zero during the early morning and evening yet still reach a sizzling 38°C at midday. Fewer than 100 days a year are frost-free and temperatures can plummet as low as -40°C. Strong northern winds can sweep across the plains for days on end, often whipping up dust storms, sandstorms, snowstorms, or (rare) rainstorms.
China's typhoon season lasts from July to October, coinciding with the heat of summer. Precipitation varies from an average of 394 mm (15.5 in) in July to only 31 mm (1.2 in) in December. The greatest rainfall and highest relative humidity occur in the southeast coastal regions, which receive an annual rainfall in excess of 1,000 mm (39.4 in). The average annual rainfall decreases to the north and northeast, dropping to a minimum of 250 mm (9.8 in) across the North China plains. China's arid northwestern provinces and western interior regions receive an annual average of less than 200 mm (7.9 in) of rain. This part of China receives its greatest rainfall in January, with an annual average of just 15 mm (0.6 in). From February through October, the average annual rainfall in northwest and west central China dwindles to about 3 mm (0.1 in).
The Himalayas act as a barrier, protecting Tibet from the rain-bearing monsoons that sweep north off the Bay of Bengal. Central Tibet sees only 25 to 50 mm of rain a year. In northern and western Tibet rainfall is even scarcer. Across the Tibetan Plateau, the "wet season" comes in July, with an average rainfall of only 122 mm (4.8 in). Precipitation is negligible in December and January. In fact, snowfall is far less common in Tibet than the name "Land of Snows" implies. The sun is quick to melt off snow falls.
Hainan Province has a tropical maritime climate with high temperatures and high humidity all year round, making it difficult to distinguish the seasons. Precipitation is heavy and evenly distributed throughout the year.
Taiwan's climate is semitropical in the north and at mountain altitudes, and totally tropical across the coastal flatlands in the south. There are two distinguishable seasons: summer, which lasts from May through October, and winter, which runs from November to March. The constant and excessive relative humidity (seldom less than 80%) tends to exaggerate Taiwan's seasons.
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