快⋯⋯了
kuài …… le
Expressing "about to happen" with "le"
快…了 says something is on the point of happening.
快 + Verb / Adj. + 了
How it works
快下雨了 — it's about to rain. 快到了 — nearly there.
快要…了 is the fuller form and means the same. Unlike 就要…了, it can't take an explicit countdown in front.
It works with adjectives too: 天快黑了.
Examples
kuài xià yǔ le
快下雨了。
It's about to rain.
wǒ men kuài dào le
我们快到了。
We're nearly there.
tiān kuài hēi le
天快黑了。
It's getting dark.