The heat

Capped swarm cells usually the bees have swarmed.
Photo by: Jim Kocherer

This hive is more than likely cooking up a swarm.

This warm humid weather is a swarm generator. Any crowded over wintered colony will very likely be cooking up some swarm cells. Regular 7 - 10 day inspections should be in place to stop the bees from swarming. Squash any swarm cells that have not been capped yet.
Capped swarm cells usually means the bees have swarmed. Make sure you can get a queen before the capped cells are squashed.
It is normal to see the bees hanging outside the hive on a hot day.
Strong colonies should have there entrance reducer out and the drawer out of any screen bottom boards.
Grass in front of the hive needs to be cut short to keep the ventilation of the hive open for fanning by the bees. A rubber welcome mat in front of the colony helps keep the grass down. A lighter color is preferable to black.