Is Hanoi very hot like the Sahara Desert? Why does the capital Hanoi suffer so terribly? First, let's compare a bit to see how hot Hanoi and the Sahara Desert are.
How hot is the Sahara Desert?
The Sahara Desert is the largest desert in the world, stretching across North Africa with an area of over 9 million km², which is about 27 times larger than the area of Vietnam. The average daytime temperature in the Sahara Desert during the summer is usually around 37 °C or more, with some places recording up to 58 °C. It's so hot that you can bake bread on the sand. However, interestingly, at night in the Sahara Desert, it is not as hot, sometimes dropping below 0 °C or lower, because the sand does not retain heat well. Snow has also been recorded in the Sahara Desert.
What about Hanoi?
Hanoi has also recorded snow in its history, but of course, not as frequently as the Sahara Desert. Hanoi is located in the northern part of our country, and Hanoi is a city with a tropical monsoon climate. The average annual temperature in Hanoi is 23.6 degrees Celsius. But this is just the average temperature for the entire summer, plus winter, plus spring, plus autumn, divided.
In the summer, temperatures often reach 30 °C, with some days hitting 40 °C or higher. What distinguishes Hanoi is that many people from other places find it very difficult to adapt here, even Westerners find it hard to adjust. This is due to the high humidity, usually at 70-80%. This humidity makes people feel like they are wrapped in a wet blanket, making the heat feel sticky and uncomfortable.
Is Hanoi as hot as the Sahara Desert?
If we only look at simple temperature numbers, Hanoi certainly does not reach the peak temperatures like the Sahara Desert. But if we consider the feeling of heat, Hanoi can surpass the Sahara Desert, making you feel exhausted. While the Sahara Desert is hot and dry, Hanoi is hot and humid, making you feel both hot and stuffy at the same time.
In the Sahara Desert, you can hide in a shady spot to reduce the heat, but in Hanoi, even if you stand in the shade, it doesn't help much because the high humidity makes evaporation difficult. Hanoi is certainly not inferior to the Sahara Desert in terms of discomfort levels.
Why is Hanoi so hot?
Hanoi is located in the northwest of the Red River Delta. The Red River Delta is a low-lying plain surrounded by large rivers. This location allows Hanoi to receive abundant sunlight year-round, as it is in the tropical zone closer to the equator than in temperate zones. The angle of sunlight in Hanoi during the summer is almost vertical, causing the heat from the sun to be extremely intense. Additionally, there are no high mountain ranges around Hanoi to protect it from the heat.
Why are places like Da Lat or Sapa cool?
Cooling occurs because altitude helps lower temperatures. On average, for every 100 m in height, the temperature drops by about 0.6 °C, but Hanoi is flat, with only a few mountains in the Ba Vi area, and the overall elevation of Hanoi is only 5-20 m above sea level. This allows hot air from the sun to easily accumulate, with no place to escape.
Another geographical reason is that Hanoi is also in an area affected by two main types of monsoons, the southeast winds and the southwest winds.
In the summer, the southeast wind from the sea blows in moisture, increasing humidity and making the air stuffy. Meanwhile, the southwest wind, sometimes referred to as the Laos wind, blows in from Laos, bringing dry heat. Hanoi is not affected as much as the central provinces, but it is still impacted.
Hanoi is influenced by many complex climatic phenomena, including El Niño and hot low pressure from the West, and there is always a factor to mention: high humidity is a major enemy in Hanoi. When humidity is high, sweat on your body cannot evaporate, making it difficult to cool down. That's why a temperature of 35°C in Hanoi can feel like 40°C or even higher. Meanwhile, in the Sahara, humidity is almost zero, so the heat, while high, is not as sticky as in Hanoi. But geography is not the only culprit. Because the heat in Hanoi also has a perpetrator: people.
Urban effects
Hanoi is a capital city with over 8 million people, filled with high-rise buildings, asphalt roads, and vehicles, turning Hanoi into a giant oven. It is always hotter in suburban areas due to the urban heat island effect. In the city center, Hanoi has countless concrete houses, with asphalt and very few trees. Concrete and plastic absorb heat very quickly, then radiate heat into the environment, causing the temperature in the city to be higher than in the suburbs by 1 to several degrees Celsius.
For example, if you step out of the inner city, many of you will see a significant drop in temperature in the suburbs because there are more fields and trees.
The next reason is that air conditioning in Hanoi makes the city hotter.
When you turn on the air conditioner, it releases hot air, raising the temperature of the surrounding air. With millions of air conditioners running loudly in the summer, Hanoi resembles a giant cauldron. Not to mention that devices like motorcycles and cars also emit heat, making the city hotter and hotter. Previously, Hanoi was cooler because there was less concrete, fewer air conditioners, less electrical equipment, and more lakes and trees. But now many lakes are no longer as pristine as before, and many trees are not as abundant as they used to be.
For example, the previous area of Ha Dong. Ha Dong had many cool fields in Ha Tay. Now it is all high-rise buildings, significantly raising the temperature. In short, Hanoi is hot not only because of nature, not only because of the sky, but also because people contribute to the heat.
Temperature records recorded by Hanoi.
First, in June 2017, a temperature of 42.5°C was recorded in Ha Dong. This was one of the hottest days in Hanoi's history. Specifically, on June 2, 2017, the Ha Dong meteorological station recorded a temperature of 41.5°C, and the next day this figure rose to 42.5°C. On the street, the actual felt temperature could reach 45 or 50°C. People in Hanoi at that time could only scream due to the scorching heat. Many even had to pour water on themselves to feel more comfortable.
Next is April 2019, which recorded a record temperature of 38.9 °C, and this was a century record. Usually, April is a cool time, but in 2019, Hanoi suddenly became hot in a difficult way. Previously, the hottest record in April was 38.5 °C, recorded in 1919. It was believed that the abnormal temperature in April 2019 was caused by El Niño and urban effects.
40.4 °C was the temperature in June 1971, and it was one of the highest milestones ever recorded in Hanoi until the 2000s. At that time, Hanoi was not heavily urbanized, so the heat was mainly from natural sources. However, for people at that time, for those who had air conditioning, fans, it was still very hot, as 40.4 °C was a terrible number.
Finally, in May 2023, Hanoi recorded a temperature of 41.1 °C. In the summer of 2023, there was a prolonged heat wave in the north. Hanoi is also known for heat spells lasting a week, even a month. For example, in a typical summer in Hanoi, temperatures continue to exceed 40 °C and often follow a series of very uncomfortable weeks.
These records show that Hanoi is not only hot but also hot due to natural and human factors. Thus, we can conclude about the comparison of the heat of Hanoi and the heat of the Sahara Desert.
The similarity is that both Hanoi and the Sahara Desert have temperatures that reach the threshold of 40 °C or higher. The biggest difference is humidity. In the Sahara Desert, there is no humidity, while in Hanoi, it is always humid. This makes the heat in Hanoi feel sticky, while the Sahara Desert has dry heat.
The next difference is in the daily and nightly temperature fluctuations. In the Sahara, daytime and nighttime temperatures can differ by 30 - 40 °C. In Hanoi, the nighttime temperature only slightly decreases, usually around 30 - 33 °C in the summer. The difference that is easy to see is the living environment. The Sahara is a desert with almost no life, while Hanoi is a bustling city with trees, rivers, and lakes, but it is affected by the urban heat island effect.
In short, although Hanoi is not as hot and dry as the Sahara Desert, the humid heat and urban effects make people feel like they are living in an urban desert. This feeling is the reason why many people feel this way.