John: 'It was sunny just an hour ago, now it's pouring rain.'
The weather's taken a turn for the worse.
C2Meaning
The weather has suddenly become significantly less pleasant.
Example sentences
Alice: 'The weather's taken a turn for the worse. I hope it clears up soon.'
John: 'The weather's taken a turn for the worse. Looks like we'll have to reschedule.'
Alice: 'We were going to have a picnic, but look at those dark clouds.'