天气预报(tiān qì yù bào) - weather forecast in Mandarin

天气预报 (tiānqì yùbào) is the weather forecast, joining 天气 (tiānqì, weather) with 预报 (yùbào, forecast, advance report). 预 (yù) means "in advance" and 报 (bào) means "to report", so 预报 (yùbào) is literally a report given ahead of time, and the whole compound is exactly what it sounds like in English.

It is a fixed four-character phrase, said as one unit rather than assembled fresh each time: 看天气预报 (kàn tiānqì yùbào), "to check the weather forecast", and 天气预报说... (tiānqì yùbào shuō..., "the forecast says...") are the two shapes you will meet constantly.

预报 (yùbào) is not limited to weather; you will meet it again in other forecasting contexts, but 天气预报 (tiānqì yùbào) itself is common enough, especially in travel and daily-routine Mandarin, that it is worth learning as a single chunk rather than building it from its parts each time.