The temperature of the hive must be kept around 35 degrees in the summer because the brood is kept in the center of the hive. At higher ambient temperatures the worker bees can use group behavior to cool the hive, saving their brood, in several ways:

The workers can carry water droplets in their mandibles to the hive and place them on the comb. Then the heat required to evaporate the water droplets is taken from the comb, thus cooling the hive.

Workers can fan the hive by beating their wings with out flying. The increased airflow allows convection to cool the hive.

A group of workers can also leave the hive to cool it down. Then there are fewer individuals that are producing heat within the hive (Cahill and Lustick, 1976).