Climate of Nanchong
Nanchong belongs to the subtropical humid monsoon climate. Compared with the Yangtze River Valley in the south of the basin, the temperature is relatively low, the rainy season is longer and the rainstorm is more. Compared with the Western Sichuan plain, the temperature is relatively high and the proportion of spring rain is large. The annual average temperature of Nanchong is about 17.1 ℃, and the annual average variation range of monthly temperature is about 4 ℃. The annual extreme minimum temperature is between - 2.5 ℃ and 5.7 ℃, and the extreme maximum temperature is between 39.0 ℃ and 41.3 ℃. In the coldest January, the monthly average temperature of all counties (cities and districts) is above 6 ℃ except Yilong, which is 4.9 ℃; in July and August, the average monthly temperature of most counties (cities and districts) is above 27 ℃. Generally, the temperature in August is slightly higher than that in July.
Among the four seasons in Nanchong, Yilong county has the longest winter, with 110 days; Shunqing district has the shortest, with only 85 days, and other counties (cities and districts) have about 95 days. Spring, summer and autumn are half a month to a month ahead of the middle and lower reaches of the Yangtze River. The frost days in Nanchong are less than 20 days, mostly 10-15 days. The longest frost days in Langzhong and southern China are only 17 days. The foggy days in Nanchong mostly occurred from October to January of the following year, especially in December, which mostly occurred from 4:00 a.m. to 9:00 a.m. The seasonal distribution of precipitation in Nanchong is very uneven. The precipitation intensity is the largest in summer, the smallest in winter, and is greater in autumn than in spring. Summer is the season with the most precipitation. The precipitation in June, July and August accounts for 28% - 34% of the whole year. The precipitation in winter is less, mainly light rain; from April, it is mainly moderate rain and heavy rain. There are many rainstorms in summer, which occur from the middle of June to the first ten days of July. According to the meteorological observation data for many years, Nanchong has a lot of night rain, and the amount of night rain exceeds the daytime rainfall, accounting for 55% of the total annual rainfall. The rate of night rain in spring was the highest, reaching 71%.
In Nanchong, the precipitation is greater than the evaporation, and the air humidity is high. The annual average relative humidity of each county (city and district) is between 75% and 79%. The average annual relative humidity is the highest in autumn, followed by winter, and almost equal in spring and summer. The extreme minimum relative humidity usually occurs in March and April in spring or December and January in winter. The air in Nanchong is relatively dry in winter and spring, which is prone to spring drought. Nanchong has a large amount of cloud and less sunshine. The average annual sunshine duration is 1369.1 hours. The distribution of total solar radiation is more in spring and summer than in autumn and winter.
The wind direction in Nanchong varies with the seasons, and is generally northerly. The wind speed in the city is small, which is a famous mild wind climate area in China. The average annual wind speed is mostly between 1.2 m / s and 1.7 m / s, and there is no wind for more than 50% of the year. However, when strong cold air invades or thunderstorm occurs in summer, strong wind often appears. Cold wave gale mostly occurs in spring. Thunderstorm gales usually occur between July and August.