Why are high clouds always thin in comparison to low and middle clouds? Why are high clouds always thin in comparison to low and middle clouds? High clouds are colder and exist where there is no water vapor, whereas middle and low clouds are warmer and have access to water vapor in the air. High clouds are warmer and exist where there is no water vapor, whereas middle and low clouds are warmer and have access to water vapor in the air. In contrast to middle and low clouds, high clouds are colder and exist among lower quantities of water vapor. In contrast to middle and low clouds, high clouds are colder and exist among higher quantities of water vapor. In contrast to middle and low clouds, high clouds are warmer and exist among lower quantities of water vapor.