When on the same day, Makurazaki in southern Japan receives 197mm of rain, Fuzhou in Fujian province of China gets 115mm, and flash floods happen in Guangdong, you may look for a connection.

Every year, spring rain, high humidity and high temperatures combine to produce a period of uncomfortable but useful weather in this part of Asia.

The southern provinces of China, the island of Taiwan, Korea and Japan all receive this weather as they experience spring and early summer.

The meiyu-baiu or "plum rain" season occurs because the southeast monsoon wind is opposed by the remains of the drier, colder late winter airmass over China. Eventually the monsoon wins and the rains move north.

Meiyu in Chinese and baiu in Japanese both mean ‘‘plum rain,’’ indicating the coincidence of the rainy season with ripening plums.

The term "meiyu-baiu", on the other hand, is believed to originate from the Chinese character for mould (mei/bai), an unpleasant effect of prolonged humid, rainy conditions.

Korea's word for this wet spell, changma, has a much simpler definition - it means "the rainy season".

Traditionally, it first starts raining in southwest China during May and reaches Taiwan and southeastern China from mid May to mid-June. The rain then migrates northward to the Yangtze River region and southern Japan during June and July, and then further northward to northern China and Korea during July and August.

This period or rain is crucial to both agriculture and water supply.

Rice transplantation in China is timed to benefit from this irrigation boost and plums fatten steadily. In Taiwan, the failure of the rains may well lead to drought conditions. South Korea receives 60 percent of its annual rainfall in this season.

Source: Al Jazeera