Why is Chengdu so gloomy every day?

Chengdu, with an average elevation of 500 meters, has typical basin climate characteristics. Affected by the subtropical monsoon climate, it is hot in summer, cool in autumn and warm in winter, with an annual average temperature of 16 and an annual rainfall of about1000 mm. The climate in Chengdu has two remarkable characteristics: first, it is foggy and the sunshine time is short; Second, the air is humid. So although the temperature is not high in summer, it looks sultry; Although the average temperature in winter is above 5℃, it is cloudy and humid, but it looks very cold. The rain in Chengdu is concentrated in July and August, and there is less rain and less ice and snow in winter and spring. Every year from March to June, September-165438+1October is the best season to visit Chengdu.