How much do clouds weigh?

The weight of a cloud depends on how you define it. It will include the weight of water droplets in the cloud itself. You may also define weight to include the weight of the air, mostly pressing down on the cloud. If only defined by water droplets, clouds have a density of about 0.5 grams of water per cubic meter. A 1 cubic kilometer cloud contains 1 billion cubic meters. That would be 500 million grams or 500 thousand kilograms. That is equivalent to 1.1 million pounds or 551 tons of water droplets.