when the balloon goes up

when (or before) the balloon goes up

when (or before) the action or trouble starts. informal
The balloon alluded to is probably one released to mark the start of an event.
1959 Punch The international rules of war are apt to be waived when the balloon goes up.
See also: balloon, goes, up

when the balˈloon goes up

(informal) when the trouble or important event begins: I don’t want to be there when the balloon goes up.
See also: balloon, goes, up
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