かと思うと・
This construction presents one situation as being followed almost immediately by a surprising development or reversal. It often feels like “just when it seemed that A, B happened.”
What the construction highlights
The important point is not merely that B happens after A. The observer has barely recognized A as the current situation when B suddenly follows or overturns it. This makes the pattern natural for weather changes, unstable behavior, rapid physical changes, and repeated swings between two states.
Rapid and surprising changes
In each example, the second event arrives before the first situation has had time to feel settled.
雨がやんだかと思ったら、今度は雹が降り始めた。
Just when it seemed the rain had stopped, hail began to fall.
Analyze弟は泣いていたかと思ったら、もう笑っている。
One moment my younger brother was crying, and the next he was already laughing.
Analyze氷を熱いスープに入れたかと思うと、みるみる小さくなった。
No sooner had the ice been put into the hot soup than it rapidly shrank.
AnalyzePast and nonpast before the pattern
A past verb commonly presents an event that has just occurred before B follows. A nonpast verb can give a more vivid view of the change as it unfolds, and it is particularly useful for recurring or unpredictable behavior. In either case, the whole sentence normally reports something observed rather than announcing a planned sequence.
Repeated unpredictable behavior
あの子は立ち上がるかと思うと、またすぐ床に座り込む。
That child will look as if they are getting up, then immediately sit back down on the floor.
AnalyzeThe nonpast verbs describe a recurring swing in behavior, not a future schedule.
Choosing among close sequence patterns
かと思うと and かと思ったら foreground the observer’s surprise or the instability of the apparent situation. たとたん ties B more directly to the exact moment A finishes and strongly favors an uncontrolled result. か～ないかのうちに emphasizes that the interval is so short that A is barely complete, without the same “just when it seemed” viewpoint. が早いか is a more written and dramatic immediate-sequence form and does not itself present A as the observer’s tentative impression.
More examples
赤ちゃんは眠ったかと思うと、すぐに目を覚ました。
Just when the baby seemed to have fallen asleep, the baby woke up again.
Analyze電車が動き出したかと思ったら、また止まった。
Just when the train started moving, it stopped again.
Analyze彼は部屋を出たかと思うと、忘れ物を取りに戻ってきた。
No sooner had he left the room than he came back for something he had forgotten.
Analyze風が弱まったかと思ったら、突然強く吹き始めた。
Just when the wind seemed to have died down, it suddenly began blowing hard.
Analyzeあの選手は元気かと思ったら、次の瞬間、膝を押さえてしゃがみ込んだ。
The athlete had seemed fine, but the next moment they crouched down clutching their knee.
Analyze猫は近づいてきたかと思ったら、さっと塀の上へ逃げた。
Just when the cat came close, it darted away onto the wall.
Analyze