Why is it so hot when it rains?

When it is about to rain, it is sultry. This is because of the high temperature and high air humidity, which leads to the slow evaporation of human sweat and makes the human body feel hot and dry.

The human body excretes sweat to achieve the purpose of cooling down. In this process, the water in the sweat evaporates, taking away the heat of the human body. But when the relative humidity is high, the evaporation rate of water will decrease. This means that the process of taking away heat from the body becomes slow, and more heat remains in the body than in dry air.

For example, people feel better in high temperature and low humidity (such as desert) than in low temperature and high humidity (such as rainforest).

Therefore, the thermal index is usually used to express the realistic heat of human body, that is, an index of somatosensory temperature is determined by combining air temperature and relative humidity.

Extended data

Factors affecting air humidity

I. Absolute humidity

There are many factors that affect absolute humidity, mainly depending on the source, transportation and the ability of air to keep water vapor. Therefore, the factors that affect water vapor supply, such as precipitation, the existence of water bodies, the level of soil humidity and evaporation conditions, the conditions that affect water vapor transport, such as wind and vertical airflow, and the conditions that affect air's ability to maintain water vapor, such as air temperature, may affect absolute humidity.

Generally speaking, the absolute humidity of tropical ocean air mass is higher than that of polar ocean air mass; At the same latitude, the humidity in the area affected by ocean air mass is higher than that in the area controlled by continental air mass. The absolute humidity in rainy season is higher than that in dry season.

The change of absolute humidity in a day is the largest in the afternoon and the smallest in the morning in coastal areas and autumn and winter, showing a single peak change; Other areas are mostly bimodal, with two high points appearing at 9 ~ 10 and around sunset respectively, and two low points appearing before sunrise and in the afternoon. The vertical distribution of air absolute humidity decreases with the increase of height.

Second, the temperature

In cold regions and seasons, air humidity is easy to reach saturation, and if the absolute humidity or water vapor pressure is not too high, the relative humidity may be higher. Under the same absolute humidity conditions, the relative humidity in warm areas and seasons is often low. The general trend of annual average relative humidity distribution in Chinese mainland is decreasing from southeast to northwest, and the mountain area is higher than the plain.

Baidu encyclopedia-air humidity

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