In my experience I have noticed 'every time' I catch a swarm, the scout bees will be readily seen investigating the trap box ahead of time. The closer to to the time of the swarm the more bees will be seen coming to and fro, in and out if the trap. I have seen trap boxes so busy that I have mistakenly assumed they were already there!
Naturally with extreme weather where flying is out of the question you will not see scout bees visiting. But at the same time, I have also noticed after the bees have been cooped up for days on end because of bad weather during swarm season, they will waste not time swarming when the rain stops. Good luck Terri, I know you are excited! I hope you catch a BIG swarm!!
Phillip