How much do clouds weigh?
Clouds can have a large range of mass per volume,
depending on how large and numerous the cloud droplets
or ice crystals are that are in them. However, they
do not really weigh anything, if by weighing you mean
putting them on a scale to weigh. Weight is defined
as the force of an object upwards as the result of
gravity. Since clouds, in a sense, defy gravity, they
do not have weight.
Clouds are less dense than dry air of the same volume.
That is why they do not fall from the sky. Upwards vertical
motions in the atmosphere also help to counteract
the weight of the droplets or ice crystals, helping to
hold them up (or make them rise even) in the atmosphere.
You can learn more about cloud mass and composition at
the USGS page at
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
Clouds weigh a lot. Although they do not weigh as much as
air. That is why they are usually buoyant - they float up high in
the air because they are less dense than air. What is interesting
is that wet (humid, that is) air weigh less than dry air. Because
we are used to thinking of water as a liquid and air as a gas this
does not seem to make sense. However, when you change water from a
liquid to a gas (water vapor or steam) it is less dense than the air
Saying that clouds weigh a lot also seems strange because we are
used to thinking of air as very light. It is that way because we
have always lived in the "sea" of air. If you drive along in your
car at 60 miles per hour and hold your hand out the window - pushing
the air out of the way - you realize that the air is quite heavy.
Have you ever flown in an airplane and felt the bumps in the
air? That is air moving and it is massive enough to move even a
heavy airplane. That rising air could eventually form a cloud (a
cumulus cloud, that is) and some of those clouds make big bumps for
the airplanes... but that is another story.
People say, "Light as air." But they are wrong.
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Update: June 2012