下小雨(xià xiǎo yǔ) - to drizzle, to be showery in Mandarin

下小雨 (xià xiǎo yǔ) is to drizzle or to be showery, built from 下雨 (xiàyǔ, to rain) with 小 (xiǎo, small, light) slotted in to soften it down to light rain.

It scales alongside 下大雨 (xià dà yǔ), to rain heavily, and 下大雪 (xià dà xuě), to snow heavily. Swap 小 (xiǎo) for 大 (dà) and light rain becomes a downpour.

British weather runs on shades of drizzle, so this phrase earns its keep: 一直下小雨 (yìzhí xià xiǎo yǔ) is that persistent, unglamorous light rain that does not quite justify an umbrella but soaks you anyway if you skip one.