when warm air mass passes over cold air mass, the water vapor in the warm air mass will condense & a warm front is when warm air mass passes over a cold air mass ->  a warm front will cause the water vapor to condense  a warm front will cause the water vapor to condense & clouds are formed by water vapor condensing ->  a warm front causes clouds to form  a warm front causes clouds to form & cloudy means the presence of clouds in the sky ->  a warm front causes the the sky to be cloudy  a warm front causes clouds to form & clouds produce rain ->  a warm front causes it to rain  a warm front causes it to rain & if it is raining, then the weather will be rainy ->  a warm front causes the weather to be rainy  a warm front causes the the sky to be cloudy & a warm front causes the weather to be rainy -> a warm front causes cloudy and rainy weather