Bees, like all insects, are ectotherms, meaning their body temperature largely mirrors the environment around them. However, a honey bee colony functions as a collective organism, capable of regulating the temperature within its nest with remarkable precision, a trait known as social thermoregulation. This ability to maintain a stable internal climate is paramount for the survival of the developing young. While bees can tolerate a wide range of external conditions, they actively work to keep the core of their home within very narrow thermal limits.
The Ideal Temperature for Bee Activity
Honey bees are most productive when the external temperature is moderately warm, allowing them to fly efficiently. The optimal temperature range for foraging activity, where bees collect nectar and pollen, is generally between 72°F and 77°F (22°C to 25°C). While they can begin foraging at temperatures as low as 54°F (12°C), their activity significantly slows down once the air temperature exceeds about 100°F (37.7°C).
This external range is distinct from the temperature bees maintain inside the hive, especially in the brood nest area. Developing eggs, larvae, and pupae are particularly sensitive, requiring a steady temperature between 91°F and 97°F (33°C to 36°C) for healthy development. Raising the brood at the warmer end of this range can result in bees that develop faster and are better foragers. The narrow requirements of the brood mean the colony is always working to fine-tune its internal climate.
Collective Cooling: How Honey Bees Regulate Hive Temperature
When the ambient temperature rises above 95°F (35°C), the colony initiates a collective cooling strategy to protect the vulnerable brood. A primary method is “fanning,” where worker bees line up at the hive entrance and inside the nest, using their wings to create an organized airflow. This concerted effort establishes an inward and outward draft, helping to circulate air and expel heat and moisture from the hive interior.
Another physical cooling mechanism is “bearding,” which occurs when a large number of bees cluster on the outside walls or entrance of the hive. This behavior reduces the total number of heat-generating bodies inside the crowded nest, which improves internal ventilation and prevents overheating. Foragers also switch their focus from collecting nectar to gathering water, which is then spread across the comb or brood cells. The subsequent evaporation of this water acts like an air conditioner, drawing heat away from the core of the nest.
The Stress of Extreme Heat and Drought
When external temperatures exceed 104°F (40°C), the collective cooling mechanisms can become overwhelmed, leading to significant stress. Prolonged high temperatures force bees to dedicate all their energy to thermoregulation, often at the expense of foraging for food resources. This shift can rapidly deplete stored resources needed to sustain the colony through the following winter.
Extreme heat combined with drought presents a double threat, as the lack of rainfall causes flowering plants to produce significantly less nectar and pollen. Internal hive temperatures exceeding 98.6°F (37°C) can cause developing pupae to become deformed or die. Temperatures over 104°F (40°C) can destroy the queen’s stored sperm, impacting the colony’s future fertility. The inability to cool the hive can also cause the wax comb itself to soften or melt, leading to structural failure within the nest.
Supporting Bees During Summer Heat
The most direct way to help bees during hot weather is to ensure they have an accessible source of clean water. Since bees use water for evaporative cooling, placing shallow dishes or bird baths filled with stones or pebbles nearby prevents them from drowning while they collect water. For managed hives, beekeepers can provide shade during the hottest parts of the day by positioning the hive under a tree or using a shade board.
Planting heat-tolerant flowers and trees can also help maintain forage availability, as drought-stressed plants produce less nutritious nectar and pollen. Minimizing disturbance or inspection of the hive during peak heat hours reduces stress and prevents the disruption of internal cooling efforts. These interventions help conserve the colony’s energy, allowing workers to focus on maintaining the delicate internal balance required for survival.