You don’t need to be a meteorologist to know that Beijing has had a fair bit of rain in recent days and weeks, or even that the summer months usually see the highest average rainfall in the Chinese capital.
However, the expertise of a meteorologist can be useful in understanding why Beijing’s rainy season starts when it does.
According to timeanddate.com, Beijing’s rainiest months have on average been June (39 millimeters), July (90.3 millimeters) and August (73.1 millimeters) between 1985 and 2015.
According to worldweatheronline.com, those averages have increased to around 73.5mm (June), 172.37mm (July) and 115.72 millimeters (August) by accounting for readings from more recent years.
However, this year has seen an increase of rainfall in Beijing from June 1 until July 1, according to the Beijing Meteorological Observatory; 111.5 millimeters of rain fell within the aforementioned time period, suggesting that the rainy season has perhaps come early.
Image via Weibo/@北京昌平
Meteorologist Wang Weiyue, from China Weather Net, explains that this is true for most parts of North China. Many places have seen a 2-4 times increase in average rainfall, Wang explains, with areas of the southeast portion of the region even seeing a 4-times increase.
The beginning dates of the rainy season in Beijing and North China have fluctuated over the years. During 1991-2000, it started around July 12; during 2001-2010, it started around July 23; and in the most recent decade, it has started sometime around late July, with the rainy season of 2020 not starting until July 28.
Why the changes? Wang explains that there are various factors including the westerly jet stream, the location and intensity of the subtropical high and the East Asian summer monsoon.
If the subtropical high moves north earlier, that means the monsoon rain goes north earlier. When the westerly jet stream is established earlier, water vapor is carried and maintained more easily.
Meteorology aside, just remember this: if you’re heading out in Beijing in June, July or August, be prepared for rain.
And, based on recent trends, the rain is arriving sooner rather than later in Beijing. But, that could all be different next year, the year after and the year after that.
Keep that umbrella and raincoat handy during the summer months (though the latter might make you sweat in the Beijing summer heat).
[Cover image via Weibo/@北京政法]