Sichuan Basin has a subtropical monsoon climate, warm in winter, dry in spring, hot in summer and rainy in autumn. The average temperature in January is 5-8℃, the average temperature in July is 25-29℃ and the annual average temperature is 15-19℃. The annual frost-free time is 280-300 days. The average temperature in January in Sichuan Basin is 3℃ higher than that in the middle and lower reaches of the Yangtze. Even the coldest days are usually above 10℃. Humidity, fog and less sunlight characterize the climate in the basin. Chengdu Plain is in the Sichuan Basin. There are 250 to 300 cloudy and rainy days a year in the plain.
The high plateau in the northwestern part of Sichuan Province is of typical plateau climate: long winter, almost no summer, less and concentrated rainfall, great difference in temperature between day and night, strong and sufficient sunlight. In contrast to the basin, the annual sunshine hours on the plateau amount to 2,500 hours. Gangzi Township, nicknamed as “the small sunshine city” on the plateau, has the most amount of sunshine hours. And Shiqu County is the “cold polar” in Sichuan Province, with the annual average temperature being only -1.6℃, the average temperature in January being -12.5℃ and the lowest temperature being -35.0℃.
In the southwestern part of the province there are high mountains and deep valleys, so people can find the vertical climate zones there. From the bank of the Daduhe River to the peak of the Gaonggar Mountain, the altitude difference is 6,500 meters. The typical plants of the different climatic zones ranging from Subtropical Zone to Frigid Zone grow there. The glacier there, 2,800 meters in altitude, is the lowest one in the same latitude zone in the world. The valleys of the Jinshajiang River (the upper reach of the Yangtze) are of the tropical climate, similar to that in Xishuangbanna in Yunan Province. In the valleys, the dry season and the rainy season are obvious, May to September being wet season and October to April of the next year being rainy season. This area is warm and sunny in winter and it is an ideal place for people to escape the cold winter in other places in China.
Sichuan Basin has the least amount sunshine time in China and its annual sunshine time varies from 900 hours to 1,600 hours. The sunshine time in the southwestern mountains changes greatly, with the lowest sunshine time being 1,200 and the highest being 2,700 hours. In contrast, the annual sunshine time in the northwestern plateau is relatively steady, ranging from 2,000 hours to 2,500 hours.
The annual rainfall in the basin is about 900 mm to 1,200 mm, but it differs from place to place. The rainfall of the area around the basin is more than that in the central area of the basin. And the mountainous area in the west of the basin has the most rainfall in Sichuan Province, its annual rainfall being 1,300 mms to 1,800 mms. Next to that, it is the mountainous area in the east of the basin, with the annual rainfall being 1,200 mms to 1,400 mms. In the central area of the basin, the annual rainfall varies from 800 mms to 1,000 mms. And also the rainfall is not equally distributed from season to season, the rainfall in winter (from December to February) accounting for 3 % to 5% of the total in a year, the rainfall in summer (from May to October) accounting for 80% of the total in a year.
It rains less on the plateau in the northwest of the province, with the annual rainfall being 600 mms to 700 mms. The plateau has obvious dry season and rainy season. The rainfall in the rainy season (from June to September) takes up 70 % to 90% of the total annual rainfall, while the monthly rainfall in the dry season (from November to April) is less than 10 mms.
The rainfall in the mountains in the southwest of the province differs greatly from place to place. This area also has clearly divided dry season and rainy season. The annual rainfall for most parts in this area is 800 mms to 1,200 mms. And the rainfall in the rainy season (from June to September) takes up 85% to 90% of the total annual rainfall.
Best time for a visit:
As far as climate is concerned, summer and autumn are the best time for touring for most scenic spots in Sichuan Province. Some visitors prefer to go to Sichuan in winter to enjoy the snow in Mount Emai and to ski in the Xiling Snow-capped Mountain.