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Creationists speculated the vapor canopy covered the earth until the first rain fell during the flood. It usually starts to get cloudy during a sunny warm day because the tops of lakes and oceans starts evaporating creating clouds. It starts to rain after a couple minutes because warm air holds more water then cool air does so when the warm air in clouds starts cooling down the moisture condenses and creates rain. Rain is not always formed on warm and sunny days but most of the time it is. It is almost always raining even though it might not be raining when you live it is raining somewhere else in the world.