Bees Bearding in Rain

I noticed bees in my one of two hives are bearding at the entrance. During the day they are around the entrance moving back and forth. The best analogy I can use is like a vacuum cleaner.

Right now its late evening and raining, but they are still out. Any thoughts on why? Are they getting ready to swarm? Hive to hot, poor circulation?

I added a super this morning to give them some room as this was a strong hive, but it hasn’t done anything as yet. Any thoughts or feedback would be much appreciated.