Clouds come from somewhere above the sky. Empty clouds are refilled by the sea. Clouds are formed by vapor from kettles. The Sun boils the sea to create water vapor. Clouds are made of cotton, wool, or smoke.
Clouds are bags of water.
Gas makes things lighter. One degree of temperature is smaller on the Celsius and Kelvin scales than on the Fahrenheit. Adult Salt added to water does not change the weight of the water.