At a glance
～たかと思ったら means "no sooner had X happened than Y" or "just when X happened, Y". It describes a second event that comes right after the first, often a surprising change the speaker notices.
[Verb た-form] + かと思ったら、[what happened next]。
子どもたちは帰ってきたかと思ったら、すぐ遊びに行った。 No sooner had the children come home than they went out to play.
How to form it
Put the verb in the た-form, then add かと思ったら.
| Verb group | Dictionary form | た-form + かと思ったら |
|---|---|---|
| う-verb | 降る | 降ったかと思ったら |
| る-verb | 寝る | 寝たかと思ったら |
| する | 勉強する | 勉強したかと思ったら |
| 来る | 来る | 来たかと思ったら |
It is used in both speech and writing. The politeness is shown at the end of the sentence: 止んだ (casual), 止みました (polite).