What are my bees doing???

[Apis629]

My hive is on two cinderblocks so it's about six inches off the ground.  The cinderblocks are standing on some bricks which I placed there to prevent one from settleing over time.  Just a few seconds ago, I saw, and counted, 26 bees standing on the ground aabout 6 inches below the enterence, fanning.  Why would they be fanning down there?  I do have a screened bottom board if that makes a difference.