Why does it always rain after work? Actually, this is not a coincidence!

Whenever we pack our things to get ready to go home, the clear blue sky always becomes overcast! Is it a curse for Bangkok residents? In fact, the causes that make it rain in the evening is not a coincidence or punishment from heaven, but it is a heat dome phenomenon caused by the actions and lifestyle of urban people. Therefore, this rain is caused by humans like us and often happens in many big cities. What is the origin of ‘official rain’? Let’s find out!

It rains because of the heat dome

Normally, the cycle of rain is caused by heat from the sun, causing ocean water and natural sources to evaporate into the air, change its state to vapor, and form thick clouds. When the air can’t support the amount of vapor, it falls as rain, returning water to natural sources again.

Nevertheless, official rain that often rains in big cities of Bangkok is quite different from normal rain because it is an effect of urban heat islands which rush the rain to rain from afternoon till evening, and always heavy downpours in the evening which is the time we get off work.

The heat dome … the congestion in a large city

The heat dome often happens in large cities with a lot of high buildings that causes the temperature in that area to be 2 – 5 degrees Celsius higher than the surrounding metropolitan area. This is because the materials used in high-rise buildings or on roads all have properties as direct heat absorbers from the sun.

Together with urban residents’ behavior, whether heat vapor from the roads or vehicles in the street, heat vapor from air compressors in thousands of high buildings which are turned on at the same time. The green areas and large trees in the city are very few in the city, so there is no sunray-absorbing agent. This is why the temperature in urban areas is higher than in upcountry, which are full of green areas.

The accumulated heat will gradually rise and spread to the side, forming a heat dome covering the city, resulting in a burning hot and sweltering temperature in the daytime. When the outside air strikes, it rains in surrounding areas which are the rim of the large city’s heat dome.

Until around 3 p.m., when the sun began to subside and the temperature began to drop, moisture in the form of heat vapor was gradually released, drifting toward cold air above the heat dome, becoming a distillation of rain called official rain.’ This is the reason why it always rains in the evening.

Therefore, stop blaming heaven and faith because this is a natural phenomenon caused by humans. We can only hope that it will rain after we get home already.

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