<p>I wouldn't say that low humidity equals more rain. The key to the conundrum is the Hadley cell. There are two of them, one on either side of the equator, and they are huge air masses which encircle the globe. What happens is that the equator is heated by the sun, and this huge mass of humid, water laden, tropical air rises to a height of about 7 or 8 miles. As it rises, the pressure falls and the air cools. Cool air at low pressure can hold less water than warm air at high pressure, so the water condenses and falls as rain on the tropical rainforest and tropical seas.</p>

<p>Thus relieved of most of its moisture, the air starts to descend, moving away from the tropics and into the sub-tropics as it does so. Warming and compressing as it passes over the desert areas which lie north and south of the tropics, it becomes much less humid and rainfall is scarce. There are other circulation cells north and south beyond the Hadley cells, but they are much less relevant to your question. Here in Hereford UK I have noticed that rain is more likely when there is high humidity.</p>

CC BY-SA 4.0
2019-10-07T09:27:46.467Z
2019-10-07T09:27:46.467Z
Michael Walsby
<p>How is that a general rule of thumb that less humidity equals more rain? Deserts don’t get much rain and humidity is also very low. Rainforests get a lot of rain when the humidity is very high so how is that that less humidity equals more rain?</p>

<rainfall><humidity>
Deserts and Humidity
Ryan Amalfitano
# Deserts and Humidity

(Asked by: username_0 on 2019-10-06)

How is that a general rule of thumb that less humidity equals more rain? Deserts don’t get much rain and humidity is also very low. Rainforests get a lot of rain when the humidity is very high so how is that that less humidity equals more rain?

**Tags:** rainfall, humidity


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## 1 answers

### Answer by username_1 on 2019-10-07. Score: 1

I wouldn't say that low humidity equals more rain. The key to the conundrum is the Hadley cell. There are two of them, one on either side of the equator, and they are huge air masses which encircle the globe. What happens is that the equator is heated by the sun, and this huge mass of humid, water laden, tropical air rises to a height of about 7 or 8 miles. As it rises, the pressure falls and the air cools. Cool air at low pressure can hold less water than warm air at high pressure, so the water condenses and falls as rain on the tropical rainforest and tropical seas.

Thus relieved of most of its moisture, the air starts to descend, moving away from the tropics and into the sub-tropics as it does so. Warming and compressing as it passes over the desert areas which lie north and south of the tropics, it becomes much less humid and rainfall is scarce. There are other circulation cells north and south beyond the Hadley cells, but they are much less relevant to your question. Here in Hereford UK I have noticed that rain is more likely when there is high humidity.


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