Beijing's spring is characterized by rapid temperature changes, little rainfall, dry and windy weather.
During spring, the subsolar point moves from the Southern Hemisphere to the Northern Hemisphere, raising the sun's altitude angle, so daylight hours become longer and temperatures gradually warm up. In spring, the mid-latitude circulation is transitioning from a radial pattern to a zonal pattern, making the atmosphere unstable. Although cold air is not as strong as in winter, there is frequent cold air activity, with more southward movements than in winter, resulting in more mobile high-pressure systems.
Due to increased cyclonic activity, weather changes are greater, leading to more windy days in spring. Beijing's plains have the highest wind speeds and most windy days in the year during spring.
The average rainfall during spring is 45 to 80 millimeters, which accounts for only about 10% of the annual rainfall. However, the evaporation rate during this period is about 30 to 32% of the annual evaporation rate. The air in Beijing is very dry with a low water vapor content, hence the saying "nine out of ten years experience spring drought".
