On hot, summer days sometimes you’ll find a large number of bees hanging on the outside of the hive. There are several reasons why this occurs including poor ventilation, overcrowding, high temps, & high humidity.
Bee bearding can often be confused with swarming. However, there are several differences. Bearding occurs in the late afternoon, whereas swarming usually occurs in the mid-morning to mid-afternoon. It is not unusual for them to beard into night time. Bearding occurs in the summer & swarming usually occurs in mid to late spring. When bearding, bees are grouped on the hive rather than flying, circling & forming a cloud ready to swarm.
It is a natural occurrence & should not be a reason for panic as long as they have room & proper ventilation. The bees move to the outside of the hive to prevent the brood from overheating.
To provide better ventilation, use top screens instead of inner covers and screened bottom boards in the summer. Routinely do your hive inspections every 7-10 days to check on brood frame count & space to prevent overcrowding.