有云(yǒu yún) - cloudy in Mandarin

有云 (yǒuyún) means cloudy, built the same way as 有风 (yǒufēng, windy) and 下雨 (xiàyǔ, to rain): the verb 有 (yǒu, to have, there is) plus an object, here 云 (yún, cloud). Mandarin weather words are mostly built this way rather than as adjectives.

有云 (yǒuyún) does not tell you whether it will rain. It just says there are clouds about; 阴天 (yīntiān), "overcast day", is the stronger word for a fully grey sky, and 下雨 (xiàyǔ) is separate again for actual rain. A weather report can string several of these together, for example 有风有云 (yǒufēng yǒuyún) for "windy and cloudy".

Because 云 (yún, cloud) is a mass noun, you never count clouds with 有云 the way you might in English ("a cloud", "some clouds"); the sentence just states that cloud is present.