How To Protect Bees In Extreme Heat

Bees can handle a hot afternoon. What they struggle with is a week of it, with warm nights that never let the hive or the nest cool down. This guide covers the story of both sides: the honeybees kept by beekeepers and the thousands of wild bee species that nobody is looking after, except perhaps you.

Heat Effect On Bees At A Glance

Why Heat Is Now A Bee Problem

Heat waves are getting longer and more frequent almost everywhere bees live. For a honeybee colony, that means burning energy and water just to keep the brood from cooking. For a bumblebee queen or a solitary mason bee, it can mean a nest that simply gets too hot to survive in.

The good news is that a lot of heat damage is preventable. A bit of shade, a reliable water source and some restraint during the hottest hours go a long way.

What Extreme Heat Actually Does To Bees

Heat hits bees in four places at once: their bodies, their brood, their homes and their food supply.

A honeybee colony keeps its brood nest at roughly 34 to 35°C (93 to 95°F), and it works hard to hold that line. When the outside air climbs past it, workers stop heating and start cooling. They fan their wings to push air through the hive, and foragers switch from nectar to water, which house bees spread in thin films over the comb so it evaporates. It is one of many jobs that fall to the same insects, and if you have ever wondered what worker bees actually do inside the hive, thermoregulation is near the top of the list. It is a clever system, but it only works as long as there is water to fetch and enough bees to fetch it. It is a clever system, but it only works as long as there is water to fetch and enough bees to fetch it.

Wild bees have no such team effort. A solitary bee sealed inside a sun-baked nesting tube, or a bumblebee colony tucked into a shallow hole in dry ground, has very few ways to cool off.

Domesticated vs Wild Bees: Who Copes, Who Struggles

Honeybees get most of the attention, but they are the best-equipped bees on the planet for handling heat. Bumblebees and many solitary bees are far more exposed.

Bumblebees evolved in cool climates. Their thick fur and large bodies are brilliant for flying on a chilly spring morning and a liability in a heat wave. Research across Europe and North America has linked hotter summers to bumblebees disappearing from places where they were once common. Solitary bees vary hugely, from desert specialists that love the heat to small woodland species that don't.

The takeaway is simple. If you keep honeybees, you have direct control. If you want to help wild bees, you work on the landscape around them: food, water, shade and places to nest.

Warning Signs Of Heat Stress

Bees tell you they're overheating long before a colony collapses. The trick is knowing what to look for, and acting at early stages instead of the emergency one.

A single sign on a hot afternoon is normal. Several at once, or signs that carry on into the evening, mean the bees are losing the battle.

Protecting Honeybee Colonies: A Beekeeper's Playbook

Your job in a heat wave is not to cool the hive yourself. It is to give the bees what they need to cool it, and then get out of their way.

1. Shade the hive, especially after midday

Morning sun helps a colony get going. Afternoon sun is the problem. Aim for dappled shade from about noon onwards.

• Plant or use existing deciduous trees on the west side of the apiary.

• Put up shade cloth (30 to 50 percent) on a frame above the hives, leaving a gap so air moves between cloth and lid.

• A spare board or sheet of plywood propped on bricks above the roof works in an emergency.

• Paint hives in white or very pale colours. Dark boxes absorb far more heat.

2. Give them water close by, every single day

On a hot day a strong colony can collect a litre or more of water. If the nearest source is far away, foragers waste energy getting there and may end up at a neighbor's pool or a polluted drain.

• Set up a water point within roughly 100 metres of the hives, ideally closer.

• Give bees somewhere to land: pebbles, floating corks, wooden chips, moss or a sloping board. Bees drown easily in open water.

• Keep it filled. Bees learn where water is and keep coming back, so a source that dries up mid-afternoon is worse than useless.

• Clean water with a trace of minerals is fine. A pinch of salt now and then is a traditional trick, as bees are drawn to slightly salty water.

3. Help the airflow, don't fight it

Bees move air in a deliberate pattern. You can support it with a few simple adjustments.

• Open screened bottom boards if your hives have them.

• Use a hive roof with vents, or shim the inner cover slightly to create a small upper gap.

• Make sure the entrance isn't blocked by dead bees, grass or debris.

• Don't drill random holes. A colony already fanning hard can lose control of its airflow if you create gaps in the wrong place.

4. Leave them alone in the heat of the day

Opening a hive at 38°C ruins hours of cooling work, can crack soft comb, and invites robbing.

• Inspect only in the early morning or early evening.

• Keep inspections short and skip the ones that aren't necessary.

• Never move hives in the middle of a hot day. If you must move them, do it at night with plenty of ventilation.

• Handle frames gently and keep them upright. Warm, heavy honey comb can tear away from the frame, and honey that leaks and picks up moisture behaves differently afterwards, which is worth knowing when you store it: how heat and moisture change honey in the jar.

5. Watch for food shortages and robbing

Heat waves often come with a nectar dearth. Hungry colonies start robbing weaker ones, and it can spread through an apiary in an afternoon.

• Heft the hive from behind. A light hive in midsummer is a warning.

• Feed 1:1 sugar syrup inside the hive if stores are low, in the evening, with no spills.

• Reduce entrances on weak colonies to make them easier to defend, but only if ventilation elsewhere is good.

• Don't leave honey, wax or frames lying around the apiary.

6. Give the colony enough room

A crowded hive traps heat and pushes bees towards swarming. Add a super or empty frames before the colony gets packed, and give space for bees to cluster without cooking the brood.

Quick Reference for Beekeepers

Helping Wild Bees Get Through A Heat Wave

You can't put a shade cloth over a bumblebee nest you've never seen. What you can do is make the patch of land you control a safer place to be when it's scorching.

1. Put out a bee-friendly water dish

This is the single easiest thing anyone can do, even on a balcony.

• Use a shallow dish or plant saucer and fill it with pebbles or marbles so the water sits just below the tops.

• Place it in partial shade, close to flowers, and away from where birds or pets drink.

• Refresh it every day or two. Scrub it weekly to stop algae and mosquito larvae.

• A patch of damp mud nearby helps mason bees, which use mud to build their nest walls.

2. Plant for late summer, not just spring

Many gardens are full of flowers in April and bare by August. Heat waves usually strike when bees need food most and find the least, and that shortage hits protein as well as nectar, since the pollen that bees pack into pellets is what feeds the next generation of larvae.

Water your flowering plants deeply in the early morning. A well-watered plant keeps producing nectar; a thirsty one stops.

3. Shade the nesting spots

• Bee hotels should face east or south-east so they catch morning sun, with shade from roughly noon. A small roof or overhang helps. In hot climates, north-east facing can be safer.

• Ground-nesting bees need some bare, undisturbed soil. Leave a few patches uncovered, ideally where shrubs or tall plants throw afternoon shade.

• Hollow stems from last year's plants are nurseries for small bees. Leave some standing rather than cutting everything back.

• Bumblebee nests in compost heaps, old burrows or under sheds should simply be left alone. Don't disturb them to "check".

4. Cut the other stresses

Heat rarely kills bees on its own. It combines with hunger, thirst and chemicals.

• Skip pesticides and herbicides during heat waves. If spraying is unavoidable, do it late evening when bees aren't flying, and never on open flowers.

• Delay mowing flowering lawns and verges. Clover and dandelions may be the only food around.

• Keep outdoor lights off at night near nests where possible.

Common Mistakes and Myths

Good intentions cause a surprising amount of harm in hot weather. These are the ones that come up most.

Building Resilience For The Long Run

One heat wave is an emergency. Hotter summers every year are a pattern, and the answer is to change the setup rather than firefight each time.

• Plant trees now. Deciduous trees give summer shade and let winter sun through. They also feed bees.

• Choose locally adapted bees. Beekeepers can source queens from colonies that have already handled local conditions, rather than stock bred for cooler climates.

• Design water in. A pond, a leaky tap over a gravel bed or a rain-fed trough is more reliable than a dish you have to remember.

• Connect habitat. Hedgerows, road verges, school grounds and farm edges link small patches together so wild bees can move to cooler spots.

• Record what you see. Notes on hive weights, dates of dearths and bee sightings help you plan, and citizen science projects use them to track bee health. In Nepal the same record keeping is what makes a single harvest window traceable from one season to the next.

Heat Wave Checklist

Print this, pin it by the back door, and tick it off when a hot spell is forecast.

For beekeepers

• Afternoon shade in place over every hive

• Water source within 100 m, with landing spots, filled daily

• Screened bottom boards open or upper vents in place

• Entrances clear of debris

• Inspections moved to early morning or evening

• Stores checked; syrup ready if there's a dearth

• Weak colonies watched for robbing

For gardeners and everyone else

• Shallow water dish with pebbles, in partial shade

• Flowering plants watered deeply at dawn

• Bee hotel shaded from midday

• Mowing of flowering patches postponed

• No pesticides during the hot spell

Final Thoughts

Bees have handled hot summers for millions of years, but never quite like this. Most of what they need from us isn't complicated: shade, water, flowers that last, and a bit of patience from the people around them. If every beekeeper shaded their hives and every garden had a water dish and some late-summer blooms, the next heat wave would be a lot less deadly for the bees that feed us.

We see the other end of this at altitude, where the honey hunters who work these cliffs report bloom and harvest shifting with warmer springs. A season's weather shows up in the jar, both in honey from a single Himalayan harvest and in the bee pollen collected alongside it.

Frequently Asked Questions

Q: What temperature is too hot for bees?
A: Honeybees start working hard to cool the hive once it passes the low to mid 30s °C (around 90 to 95°F). Above about 40°C (104°F), comb softens and colonies without shade or water are at real risk. Many bumblebees struggle from the mid 30s °C.

Q: Why are bees hanging on the front of my hive at night?
A: That's bearding. The colony is moving bees outside to keep the inside cooler. It's normal in hot weather, but if it happens every night, check shade, ventilation and space.

Q: Should I put ice on my hive?
A: No. Sudden cold and dripping meltwater cause more problems than they solve. Shade and water are safer and more effective.

Q: Can I help wild bees if I only have a balcony?
A: Yes. A pot of drought-tolerant herbs, a pebble-filled water saucer and a small bee hotel in morning sun make a real difference especially if you’re in a city.

Q: Do bees fly in extreme heat?
A: Honeybees keep flying, especially for water, though foraging often drops during the hottest hours. Many wild bees shift their activity to the cooler morning and evening.

References

• White SA, Dillon ME. Climate warming and bumble bee declines: the need to consider sub-lethal heat, carry-over effects, and colony compensation. Front Physiol. 2023 Oct 31;14:1251235. doi: https://doi.org/10.3389/fphys.2023.1251235. PMID: 38028807; PMCID: PMC10644220.

• Jitesh Jhawar, Jacob D. Davidson, Anja Weidenmüller, Benjamin Wild, David M. Dormagen, Tim Landgraf, Iain D. Couzin, Michael L. Smith; How honeybees respond to heat stress from the individual to colony level. J. R. Soc. Interface. 1 October 2023; 20 (207): 20230290. https://doi.org/10.1098/rsif.2023.0290 

• Zhao, H., Li, G., Guo, D. et al. Response mechanisms to heat stress in bees. Apidologie 52, 388–399 (2021). https://doi.org/10.1007/s13592-020-00830-w