Whew is used in writing to represent a sound that you make when you breathe out quickly, for example because you are very hot, very relieved, or very surprised.
[feelings]
'Whew,' he said. 'It's hot.'
You were just in time. Whew! What a close call.
'Whew! What is that terrible smell?' she cried.
whew in British English
(hwjuː)
exclamation
an exclamation or sharply exhaled breath expressing relief, surprise, delight, etc
whew in American English
(hwju; hju)
interjection
used to express variously relief, surprise, dismay, or disgust