Beekeeping in Hot Weather: How Bees Cope at 47°C

During an extreme heat wave that reached 47.4°C (117.3°F) in full sun, healthy production colonies and nucleus colonies kept their brood close to 35–36°C. Weaker, broodless and drone-laying colonies showed much greater temperature swings, while fresh nectar stores may have helped the strongest colonies buffer the heat.

Following colonies through one of the hottest weeks ever recorded.

Every summer seems to bring another record-breaking heat wave. For beekeepers, these events naturally raise concern. Can honey bee colonies continue to protect their brood when temperatures climb well above 40°C? At what point does the heat become too much, and should we intervene?

During one of the hottest periods ever recorded in our region, our weather station measured 47.4°C (117.3°F) in full sun near the apiary. Rather than speculate, we decided to let the sensors tell the story.

Over the course of the heat wave, BroodMinder sensors continuously monitored colonies installed in wooden, polystyrene, and plastic hives. Some were strong production colonies, others were smaller nucleus colonies, while a few were weak or broodless. Together, they provided an opportunity to observe how different colonies coped with exceptional conditions in real life—not in a laboratory.

The video follows the event as it unfolded. The first part was filmed during the second day of the heat wave, while temperatures were still climbing. Several days later, once the weather had returned to normal, we revisited the apiary to review the data and discuss what we had learned.

The Bees' Air Conditioning System

Honey bees have evolved remarkable mechanisms to regulate the temperature of their nest. Unlike us, they cannot seek shelter indoors or switch on a fan. Instead, the colony works collectively to keep the brood nest close to its ideal temperature of 35–36°C (95–97°F), regardless of what is happening outside.

Thousands of workers participate in this effort. Some ventilate the hive by fanning their wings, while others collect water that can be evaporated to remove excess heat. Together, they create an incredibly efficient natural cooling system.

That said, this cooling comes at a cost. Every bee dedicated to ventilation or water collection is one less bee available to forage. During prolonged heat waves, maintaining the hive's climate becomes a significant part of the colony's daily workload.

Beekeeping in Hot Weather: Healthy Colonies Keep Their Cool

Throughout the heat wave, BroodMinder sensors continuously recorded brood temperature while a weather station measured ambient conditions nearby.

The first chart combines four healthy production colonies. The dashed green curve shows the outside temperature, while the solid lines represent brood temperatures measured inside the hives. The shaded gray area indicates the Brood Zone™, the temperature range required for healthy brood development.

The result is striking. While the outside temperature followed a dramatic daily cycle—approaching 47°C every afternoon before cooling again overnight—the brood temperatures barely moved. All four colonies remained comfortably within the Brood Zone, fluctuating by little more than a degree.

This is perhaps the most reassuring result of the study. Healthy colonies proved extraordinarily effective at protecting their brood despite experiencing one of the hottest periods of the summer. The outside temperature changed by more than 20°C every day, yet the brood nest remained remarkably stable.

When Thermoregulation Becomes More Difficult

Not every colony behaved the same way. The next chart shows several weaker colonies, including broodless and drone-laying colonies. Here, the difference is immediately visible.

Instead of remaining tightly grouped around the ideal brood temperature, these colonies experienced much larger daily fluctuations. They were still capable of buffering the outside conditions, but clearly not to the same extent as the stronger production colonies.

Without a large brood nest requiring precise temperature regulation—or simply without enough workers available to manage the hive's climate—the internal temperature became noticeably more variable. Therefore, colony condition and population appear to play an important role in resilience during periods of extreme heat.

Nucleus Colonies Also Maintained Stable Brood Temperatures

Nucleus colonies are often considered more vulnerable during periods of extreme heat because of their smaller populations. During this study, however, the monitored nucs maintained brood temperatures well.

Although their populations were smaller, brood temperatures remained comfortably within the Brood Zone throughout the heat wave. Under the conditions of this study, they showed no particular difficulty maintaining brood temperature despite the exceptional weather.

These results should not be generalized too broadly. Nevertheless, they show that colony size alone does not determine thermoregulation. A healthy nucleus colony can maintain a stable brood nest under demanding summer conditions.

Context Matters

Every field observation comes with context. This heat wave occurred immediately after the linden honey flow, when the production colonies were carrying supers heavily filled with fresh nectar.

This detail matters because freshly collected nectar contains a significant amount of water. Besides providing thermal mass, it also offers an immediately available water source for evaporative cooling inside the hive. Consequently, the colonies may have needed to collect less water from outside than they would later in the season.

For this reason, these observations should not automatically be extrapolated to late-summer colonies carrying fully ripened honey or experiencing nectar dearth. One of the strengths of field studies is that they reflect real conditions—but real conditions always deserve careful interpretation.

Should Beekeepers Be Worried During a Heat Wave?

Overall, the results are reassuring. Strong, healthy colonies demonstrated an impressive capacity to regulate brood temperature, even under exceptionally challenging conditions. Honey bees possess sophisticated thermoregulation mechanisms, and the data show how effectively these mechanisms can protect developing brood.

That said, the study also highlights that colony strength matters. Weaker colonies have fewer resources available for climate control and therefore deserve closer attention during periods of extreme heat.

Perhaps the most useful conclusion was that, in the healthy colonies we monitored, the bees themselves were not necessarily the weakest point in the system. The hive equipment was still absorbing a considerable amount of solar energy.

The Next Question: Can We Reduce Heat Entering the Hive?

While reviewing the data, another observation stood out. Although brood temperatures remained stable, hive roofs absorbed large amounts of solar energy throughout the day. If we could reduce that heat before it entered the hive, perhaps we could reduce the cooling effort required from the colony.

That question became the starting point for the next article in this series. We tested a centuries-old Mediterranean practice—limewashing hive roofs—and measured exactly how much difference it made.

Read the next study: Limewashing Beehive Roofs—How Much Cooler Do They Really Stay?

Explore the Heat-Wave Data

The video tells the story, while the BroodMinder dashboard lets you inspect the measurements. Use the interactive dashboard below to explore brood temperatures, weather conditions and colony productivity throughout the heat wave.

Open the interactive dashboard in a new tab

Key Takeaways

• Healthy production colonies maintained brood temperatures close to 35–36°C, even when the weather station reached 47.4°C in full sun.
• The brood nest remained remarkably stable despite daily ambient temperature swings exceeding 20°C.
• Weaker, broodless and drone-laying colonies followed ambient conditions more closely.
• Under the conditions of this study, healthy nucleus colonies also maintained stable brood temperatures.
• Fresh nectar stores likely contributed to thermal buffering and evaporative cooling and should be considered when interpreting the results.

BroodMinder Summer Beekeeping Series

This article is part of the BroodMinder Summer Beekeeping Series, where we use real-world sensor data to understand how honey bee colonies respond to hot summer conditions and evaluate practical, evidence-based solutions for reducing heat stress.

• When Temperatures Reach 47°C: How Do Honey Bee Colonies Cope? (this article)
• Limewashing Beehive Roofs: How Much Cooler Do They Really Stay?
• Which Hive Material Stays Coolest in the Sun? (coming soon)

Every Hive Counts.

The BroodMinder Team