Vermicomposting during heatwave : Tips to safeguard your worms

Here are the tips to maintain vermicomposting and care for your worms during summer and heatwave periods.

As temperatures rise and heat waves become more frequent, it’s crucial to safeguard not just yourself, but also your worm composter and its inhabitants from the scorching heat. In this guide, we’ll explore what happens inside a worm composter during high temperatures and provide a “heat wave plan” to ensure your worms thrive in the summer heat.

The increasing prevalence of heatwaves necessitates measures to protect not only ourselves but also our worm composters during the scorching summer months. Much like humans, worms require care and attention to endure extreme heat successfully. In this article, we will delve into the intricacies of maintaining a worm composter during high temperatures and unveil an effective “heat wave plan” to safeguard your worms’ well-being.

Understanding the impact of heatwaves on vermicomposting:

A heatwave is defined as a period of sustained high temperatures lasting for at least three consecutive days and nights. During such spells, the atmosphere fails to cool down adequately, intensifying the heat’s effects.

For optimal composting performance, worms and the entire composting ecosystem thrive within a temperature range of 15°C to 25°C (59°F to 77°F).

Below this range, the ecosystem operates at reduced efficiency, while temperatures above 35°C (95°F) can prove fatal to the worms.

temperatures for vermicomposting

Effects of high heat on worm composters:

Decomposition of waste

In scorching temperatures, when the composting ecosystem struggles to function efficiently, other organisms step in to decompose organic waste. This alternate decomposition process, driven by bacteria, demands copious amounts of oxygen, creating an inhospitable environment for your worms. Moreover, this process alters the consistency of fresh raw materials, rendering them soft or liquid, which attracts midges !

Bedding and environmental parameters in vermicomposting:

Enclosed composters tend to trap heat, and inadequate ventilation exacerbates this issue. Proper airflow is essential to dissipate excess heat. Moisture in the bedding acts as a “heat-transfer fluid,” meaning higher moisture levels result in hotter bedding. As the bedding acidifies due to bacterial activity and reduced oxygen, it becomes less suitable for the beneficial organisms involved in vermicomposting.

If your composter is not ventilated enough because of reduced airflow, packed bedding, many stacked trays, then, the heat builds up.

It’s like a heat wave inside the composter !

The moisture in the bedding works as a “heat-transfer fluid”. The higher the moisture is, the hotter the bedding gets.

The bacteria at work acidify the bedding and this process is increased with the lack of oxygen. Therefore, the bedding becomes far less hospitable for the “good” organisms of the vermicomposting.

Do not hesitate to visit this page for further information.

How to recognize heat stress in worms:

  • Above 25°C (77°F), worms and other organisms exhibit reduced feeding activity.
  • At 30°C (86°F), worms seek cooler areas within the composter, such as along the sidewalls or beneath the lid. They may also migrate to the collector tray, which offers higher humidity and cooler conditions.


extreme temperature
worms got hot

When temperatures reach 35°C (95°F), worms attempt to escape the extreme heat by exiting the composter, often landing on a dry surface, where they quickly desiccate and perish.

This scenario is not only distressing but also generates unpleasant odors and attracts maggots.

The Comprehensive “Heatwave plan” for vermicomposting:

To safeguard your worm composter from extreme summer heat, follow these proactive steps:

Provide shade and cool shelter:

Place your composter in a shaded, cool location, such as a cellar, laundry room, or basement. This move ensures that your worms don’t endure the blistering heat.


Would you yourself stay outside all day when it is so hot ?

Reduce waste input:

During hot weather, organisms within the composter consume less. Minimize waste input to prevent problems arising from inadequate decomposition. Consider adding thick cardboard to absorb excess moisture and aerate the bedding. Ground eggshells can also be beneficial.

The waste won’t be processed by the worms anymore but by some bacteria which will consume the oxygen. As soon as the fermentation starts, the waste get warmer and warmer.

So the good strategy is to stop adding any waste, or at least very little, in order to avoid the problems.

When it’s hot, what do you prefer ? A raclette or a light salad ?

Enhance ventilation in worm composter:

Ensure your composter is well-ventilated, especially if it’s enclosed. Use pieces of brown corrugated cardboard to promote airflow. If your composter features a spigot, keep it open, but remember to place a container underneath. For non-spigot models, empty the collector tray regularly to reduce moisture.


ventilation worm composter

Create some ventilation shafts to ensure proper aeration between the different trays. You only have to make a hole by pushing the waste material on the side. Good airflow allows the composter to cool down and to get rid of the excess of moisture.

inside worm composter
ventilation for worm composter in summer

Create a cool refuge:

Worms seek refuge in cool areas. Prepare a “Fresh Zone” by emptying the collector tray, placing cardboard or a damp cloth in half of the tray. Adequate ventilation is crucial for maintaining the right humidity level without excess moisture.

Now, it’s your turn to get this ‘Fresh Zone ready !


Empty the collector tray, put some cardboard or a wet cloth in half of the tray. The evaporation has a cooling effect and this ‘fresh place’ will even be cooler if it is well ventilated.

This ‘Fresh Zone‘ must be humid enough to welcome the worms but not too humid to allow a good evaporation effect.

good temperature for worms
summer plan for worm composters
cool aera in vermicompost

Introduce cool elements in worm composter : summer Menu !

Consider refrigerating kitchen scraps before adding them to the composter. This cools the composter while avoiding issues associated with frozen waste. Additionally, you can place ice packs or frozen water bottles on top of the composter or within the waste, but be cautious of moisture buildup.

Be careful : do not put the waste in the deep freezer to cool down the composter afterwards.

Indeed, kitchen scraps contain a lot of water. When it turns into ice, the frozen water breaks the cell membranes. Then, the thawing process releases a lot of water very quickly and this can hamper the composting process.

The evaporation has a cooling effect. At school, we were told that water needs some energy – heat – to change from the fluid to the gaseous state. So when water evaporates, it cools down the composter. It absorbs the heat and turns itself into a low-temperature vapor.

If your composter is very well ventilated, you may think of putting a wet cloth or pieces of brown cardboard at the top of the compost. The ventilation will allow evaporation which will cool down the place a little bit. But forget about it if the whole system is not well ventilated because it would only add some more moisture and that’s not something you want.

Another strategy is to put an ice pack or a frozen water bottle outside on top of the composter or just on the waste inside. But be careful because it will also bring some moisture from condensation. So do not hesitate to add quite a lot of pieces of dry brown cardboard.

Is that enough to get the worms safely through the heatwave ?

Not too much moisture and good ventilation is what a vermicomposter needs to get through extreme heat.

Here are the tips to repeat over and over again when it’s very hot.

Keep an eye on your wrigglers. Avoid the sunlight !

Renew the material in the ‘Fresh Zone’ because it will soon turn into some compost.

Do not add too much food.

By implementing these strategies to manage extreme summer heat in your worm composter, you can ensure the well-being of your worms and maintain an efficient vermicomposting system, even during heatwave. Ultimately, reducing waste through composting contributes to environmental sustainability by mitigating greenhouse gas emissions.

Do not hesitate to share your tips and good strategies to manage the vermicomposting during heatwaves.

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  1. Pablo

    I live in Central Arizona “It’s a dry heat.” :D) Today’s high was 106 degrees. My worm bin is in a bath tub and gets up to 88 degrees, but only for an hour or so each day, it doesn’t stay there. There was a day where my bin got up to 95 degrees, but thankfully only for a short time (just once). That was before I got serious!!! Thank god my worms are still alive. When I built my bin it was last Fall. I wasn’t too concerned then as the lowest temps got into the 40s. I even installed a heat mat, worked great through the winter months. I also installed a temperature monitor Wi-Fi so I’m now aware of my temperature (Yolink) and am able to monitor my bin much more closely.

    Now, when the temperatures are so extreme, I do several things; I place frozen milk jugs (2-3) in the morning around 5 AM across the top of the compost. I then close my bin (open at night) and reinsulate (cardboard, plus foam, insulated reflective cover). Close up shop basically. I do a second replacement of frozen jugs around noon (each day). I recycle (refreeze) the jugs. I mentioned I open my bin entirely at night to cool things down. I also installed a shade sail on the west side. I have my worm bin under a Mesquite tree (not the best choice) and I should have put it under a denser shade tree. I’ll probably move the bin this Fall to a better more shadier location.

    I understand folks do different things when it’s hot. I believe “Mass” (size matters) of your bin is the key. Depending upon the size of your bin will determine how much the temperature can fluctuate in your bin. Obviously, keeping your bin indoors is probably the best idea for small worm bins. Larger bins like Captain Matt (YouTube) he keeps his in his garage. Of course he lives in Massachusetts? The Arizona Worm Farm (Phoenix) maintains their worms in large piles of wood chips, plus produce, with fans, under a metal roofed structure with fans blowing on the piles. Pretty cool operation (no pun intended).

    • David

      Hello Pablo,
      Thank you very much for sharing your experience.
      Nothing beats advice from other users!

  2. Nancy Kennedy

    I live in a very hot area of Australia. Way too hot for worms so I keep my worm farms inside with the A/C, where the temp is in the 20’s C. They don’t smell and they are easy to monitor and feed.

    • David

      Good job!

  3. Wigglewigglewiggle

    Thanks for the tips the “island” part especially inspired me to use some paper towel cardboard roll with some carboard paper stuffed inside to create a literal elevator that’s well ventilated in my small kitchen counter worm bin. It has otherwise no aeration and no multiple layers so it would be very hard to ventilate like for bigger worm bins, but the island tip was really a nice way to put it!

  4. Mihwa

    Thank you for the great tips. I am a new worm mom and the first summer is hitting here in Arizona where it will hit 114F this weekend. I will put some moist hay in the bottom of the bin tomorrow.

    • David

      Take care off them !

    • Mihwa

      When I checked the bin last Saturday when it was 112 F-113 F, my wormies were doing ok. They were chilling under the hay in the bin. Yesterday, the temp hit 114 F here in AZ. But I didn’t check the bin for them yesterday. Today, when I opened the bin, all the wormies were disappeared. I mean there is ZERO worms. I don’t even see a dead body. Why is that? My father-in-law says when it’s too hot they “melt”. Is it true?

    • David

      This temperature is indeed much too high for the worms.
      Where is the vermicomposter placed? The worms could have escaped into the soil if it was possible for them to do so (or die at the bottom of the vermicomposter).
      If the worms have “liquefied”, it must smell very bad in the vermicomposter. In this case, you need to empty it to clean it (you can use the vermicompost that is still good for plants).

  5. Patricia roe

    I have already learned how to protect worms in compost from heat. I live in Florida.

    • David

      Great! What tips would you add to protect worms from the heat?

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