Science - Weight of clouds

The U.S. Government Geological Survey states the following:

"Do you think clouds have any weight? How can they, if they are floating in the air like a balloon filled with helium? If you tie a helium balloon to a kitchen scale it won't register any weight, so why should a cloud? To answer this question, let me ask if you think air has any weight—that is really the important question. If you know what air pressure and a barometer are, then you know that air does have weight. At sea level, the weight (pressure) of air is about 14 ½ pounds per square inch (1 kilogram per square centimeter).

Since air has weight it must also have density, which is the weight for a chosen volume, such as a cubic inch or cubic meter. If clouds are made up of particles, then they must have weight and density. The key to why clouds float is that the density of the same volume of cloud material is less than the density of the same amount of dry air. Just as oil floats on water because it is less dense, clouds float on air because the moist air in clouds is less dense than dry air.

We still need to answer the question of how much a cloud weighs. To confuse things more, the weight depends on how you define it:

• The weight of the water droplets in the cloud
• The weight of the water droplets plus the weight of the air (mostly above the cloud, pressing down)
  

We're only going to look at the weight of the actual cloud particles. One estimate of cumulus cloud density is given at https://www.sciencealert.com/this-is-how-much-a-cloud-weighs, as a density of about 0.5 gram per cubic meter. A 1 cubic kilometer (km3) cloud contains 1 billion cubic meters.

Doing the math: 1,000,000,000 x 0.5 = 500,000,000 grams of water droplets in our cloud. That is about 500,000 kilograms or 1.1 million pounds (about 551 tons). But, that "heavy" cloud is floating over your head because the air below it is even heavier— the lesser density of the cloud allows it to float on the dryer and more-dense air."

Qur'an - Weight of clouds

Qur'an clearly states that the clouds are heavy!  The weight of the clouds was not known 1400 years ago.  On the contrary, people were thinking that the clouds are light and that's why the wind moves them in the sky.

هُوَ ٱلَّذِى يُرِيكُمُ ٱلْبَرْقَ خَوْفًا وَطَمَعًا وَيُنشِئُ ٱلسَّحَابَ ٱلثِّقَالَ

It is He who shows you lightening, [causing] fear and aspiration, and generates the heavy clouds.  13:12

وَهُوَ ٱلَّذِى يُرْسِلُ ٱلرِّيَـٰحَ بُشْرًۢا بَيْنَ يَدَىْ رَحْمَتِهِۦ حَتَّىٰٓ إِذَآ أَقَلَّتْ سَحَابًا ثِقَالًا

سُقْنَـٰهُ لِبَلَدٍ مَّيِّتٍ فَأَنزَلْنَا بِهِ ٱلْمَآءَ فَأَخْرَجْنَا بِهِۦ مِن كُلِّ ٱلثَّمَرَٰتِ كَذَٰلِكَ نُخْرِجُ ٱلْمَوْتَىٰ لَعَلَّكُمْ تَذَكَّرُونَ

And it is He who sends the winds as good tidings before His mercy until, when they have carried heavy rainclouds, We drive them to a dead land and We send down rain therein and bring forth thereby [some] of all the fruits. Thus will We bring forth the dead; perhaps you may be reminded 7:57