Partly cloudy, a technical term, is when the cloud cover is between 31 and 70 percent. This is an interesting expression simply because so many people guess wrong about its origins. They're willing to bet that it was born at the racetrack, where any part of a horse that extends over the finish line first is enough to make it a winner. Given the shape of a horse, that has to be its nose. When broadcasting began, directors had to communicate with people on the air without making noise, so they developed hand signals.
Time is always a key element in live broadcasts.
The person at the mike needed to know if the program was on schedule.