趁热打铁用英语怎么说？

to strike while the iron is hot:
Take advantage of favorable circumstances while they last. The image is from a blacksmith’s shop; the smith can shape iron only by striking it with his hammer when it is red hot.
It means to take action at the right moment.
从字面意思可见，这个短语的意思是“趁热打铁，抓住有利时机做（某事）”

Example:
As soon as John heard that his father had won in the lottery, he struck while the iron was hot and ask for an increase in his allowance.