Honeybees keep their brood nest within a tight band around 34–36°C regardless of the weather outside. In summer heat, the colony's main defence is not insulation but active ventilation: bees fan air through the entrance, spread droplets of water to evaporate, and cluster ("beard") outside the box to remove their own body heat from the interior. Beekeepers help by widening entrances, adding shade and providing a reliable water source nearby.
On the hottest days a strong colony can pull tens of thousands of individual foraging trips just for water, and if the wax comb ever exceeds roughly 40°C it can soften and collapse — which is why overheating is treated as seriously as winter cold by experienced beekeepers.
A cutaway 3D Langstroth hive where widening the entrance vent, adding a shade cloth and providing a water source cool a simulated internal temperature that responds live to outside heat.
Internal hive temperature depends on outside air, solar gain and metabolic heat from the colony, offset by convective ventilation through the entrance and evaporative cooling from water bees fan through the moving air.
Raise the outside temperature to simulate a heatwave, then open the entrance vent, add a shade cloth and switch on the water source to see the thermometer gauge and colony status respond in real time.
Wax comb can start to soften and sag once hive temperatures pass about 40°C, so on the hottest days a colony's fanning and bearding behaviour is really an emergency structural repair crew as much as a cooling system.