There are several synonyms that can be used in place of "are overcast." These include "cloudy," "gloomy," "dull," and "overcast." Each of these words conveys a slightly different shade of meaning, but all describe the same basic condition of the weather. "Cloudy" implies a cover of clouds, "gloomy" suggests a somewhat depressing or sad atmosphere, while "dull" evokes a sense of lifelessness or lack of color. "Overcast" specifically refers to a sky covered in clouds, while the other words can also describe other aspects of the environment, such as temperature, brightness, or mood.