When the balloon goes up

The time during the doning of the condom.

Signifying that things were getting serious and action could occur soon.

Popularized use of observation balloons during the first World War. The sight of such a large balloon going up nearly always resulted in a barrage of juice/shells following soon after.

The expression was re-inforced during WW2 when the hoisting of barrage balloons was part of the preparations for an air-raid notifying the gunners it is safe to to open fire.

Chuck always gets excited when the balloon goes up.

I heard the ballon was going up over at your place the other day. Yeah, I heard that Xi put the balloon up quickly and Biden wasn't quite ready to take it.

President Biden when Xi's balloon went up:

"We’re Going to Take Care of It"