Angus StewartFour tips to keep your worm farm cool on hot days

Make your worm farm the coolest one in the neighbourhood! After twenty years of running a worm farm at home I can honestly say it is one of the easiest ways to compost your kitchen scraps. The worms are very good at looking after themselves, even if left to their own devices for several weeks at a time they will happily survive and then thrive once you are back to feed them again. However, I did have one incident early in my vermiculture career many years ago where I lost all my worms in a single day when the mercury tipped over the 40 degrees C (104 F) mark on a blistering summer’s afternoon.

How to protect your worm farm in hot weather


Unfortunately, the worm farm was in direct sunlight that day and as the worm farm is black in colour, it absorbed the maximum amount of heat and it got way too hot for the poor worms inside. Sadly, I had to start again and bring in a whole new population of worms.

Having learnt a lesson from my one and only disaster as a worm farmer, I can suggest the following precautions to help your worms keep their cool.

1. Keep your worm farm in a shady spot in the garden. Under a deciduous tree is good because when the tree loses its leaves in winter the worm farm will benefit from a bit of direct sunlight to warm it up a little during the cooler months.

2. Keep it in an indoor spot that does not get too hot in summer , or too cold in winter. A garage , garden shed or laundry can all provide a good home.


3. If you have advanced warning of a heat wave, drape some hessian (or similar absorbent material) over the worm farm and keep it moist. As moisture evaporates from the hessian it will cool the worm farm in a similar way to that great Australian invention for kitchens in electricity deficient parts of the outback, the ‘Coolgardie safe’.

4. Paint your worm farm a light colour so it reflects more heat. This can be a fun project for the kids as they can use their imagination to create their own unique worm farm.


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Angus Stewart

About Angus Stewart

Gardening Australia TV presenter, author of 'Creating an Australian Garden', 'Australian Plants for Year-round Colour' and 'Let's Propagate', garden travel guide, native plant specialist and breeder. Central Coast, NSW. Find out lots more about native plants at Gardening with Angus.

25 thoughts on “Four tips to keep your worm farm cool on hot days

  1. I had the loss of my worms as a result of the extreme hot weather.
    I put two layers of carpet directly on top of the worm food and kept adding water then the black plastic lid, seems to be doing the job.

  2. I had the same experience this summer even though my worm farm was in shade. I managed to rescue some (the lower tray) and next time, plan to break all the trays up & put them in a single layer on the ground in the shade when we have another really hot day. It seems they can then at least escape to the cooler earth underneath if necessary.

  3. Great advice(as always) especially as most articles on compost advise putting them in full sun. My black plastic triangular one only receives about three hours of morning sun and receives all my kitchen green waste and occasional deciduous leaves and operates so well. Every one should have a compost bin even it is just for kitchen green waste and nothing else.

  4. I had a similar experience, we shifted house on a 40 degree day in January & my worm bin was place unbeknown to me in full sun on concrete. When I discovered it every single worm was out of the bin on the concrete in a massive wormy pile at the foot of the bin. I very hurriedly moved it into shade, put all the worms back in it & watered it, amazingly my worm bin was back to maximum working capacity in about 3 weeks. They really are incredible little critters!

  5. 3/15/2013 1615
    hello my name is Chuck i just starting my worm farm i live in n. Tx
    if my worms get too warm i will get a bag of crushed ice from Sonic, put
    some on top cool water too, dont use too much
    common sense

  6. Summer protection for worm farms – Shade and lots of bedding!

    Hello I have run worm farms for many years in South Africa and it can really get hot here. So far I hardly ever lost worms due to hot temperatures!

    Worm farms can overheat when exposed to the sun on very hot days so it is generally a good idea to set up your worm bins in an area where you can provide them at least with some shade.

    There are many ways you can go about this. You can place bins under trees, in a garage, a store room under a sun roof, in an alley that gets only very little sun or any other place on your property that gets only exposure to the sun either in the morning or late afternoon when the impact of the sun is not that strong.

    Should you not be able to make use of any of the above mentioned options which are basically free of charge, than you should provide your worms with some custom build sun cover.

    Second hand carpets on top of a worm bin are a good and inexpensive solution. If you can’t get hold of carpets or blankets you might have to consider setting up a roof of shade cloth that you can purchase from most large nurseries and Garden suppliers.

    This is obviously a more costly solution and in my opinion not needed if one takes advantage of one of the no cost or low cost solutions mentioned before.

    Should the temperatures be above 35 C / 95 F in the shade than it becomes really dangerous for your worms.

    In this instance you should consider to fill up your worm farm with as much bedding as possible.

    I would suggest a mix of compost and worm castings that should be just slightly wet would be fine.

    This additional bedding will act as an insulator against extreme temperatures and might give the worms the opportunity to hide in the center of the worm farm furthest away from the heat.

    Another way would be to pour cold water regularly over the worm bedding during the heat of the day! But apart from being time consuming you will have to find out how long it will take for the bedding to worm up again. Soggy bedding can heat up much more than dryer bedding. So I would be careful with this method!

    Proper aeration of the worm bin is another important factor. The air inside the worm bin needs to have a way to get out of the bin!

    I hope this helps

    Happy worming
    kind regards


    • Hi Stephan
      Unfortunately we go away every year for a week in the hottest part of the year. Gets to 40+ degrees. I’m not sure what to do then. My compost bin is where I have them. I take the lid off when it’s hot and cover it with an old light coloured curtain to let the heat out and provide shade. Any suggestions for when I go away? I’ve thought maybe frozen bottles left upside down. But the ice will only last a day I would say..

      • Hello Angela, as I mentioned in my previous post it it is important to add as much processed bedding as possible to your bin, which will act as a natural insulator and will give your worms an extra protection against the hot temperatures. Another thing you can do is to build a polystyrene box that you can place your worm bin in. The box should have a lid and you should make a few small holes near the top of that box to let any warm air out as well. Apart from that it is very important to have the box standing in the shade and protected from direct sun at all times.

        I hope this helps Angela. Here in Cape Town we get as well often days in the heat of summer where we experience 40+ degrees and my worms have always made it.

        Have a great day and enjoy your time away.

        Kind regards and blessings


        • What is processed bedding Stephan? I always put my moistened egg cartons in there which they love.
          FYI I have been to Cape Town as a child for a holiday. We stayed in Fishoek (I’m not sure if that’s the right spelling).

  7. I have lost my worms too even though my worm farm has partial morning sun and it is covered with a thick wet towel and a foil insulated sun shade. With the recent 40 plus temperature I made a large ice block. Size of a 2 litre ice cream container. I put the ice block inside the top level and covered it with the castings and a wet tee shirt and the ice would take 10 hours to melt completely. The cold water dripped down to the lower levels and out through the tap into a bucket. This kept the worms cool and they all congregated “upstairs” to be near the ice and food. At night I put a smaller ice block if it’s a hot night. I find this method very easy and I only have to check the worm farm twice a day .

  8. Hi Angela ,
    My worms in the bottomless compost bin survive very hot weather because they travel to the bottom which is cooler.. Water well and place a thick layer of wet newspapers and wet towel on top of the compost. Leave the lid off and cover the bin with your curtain like you have done before.
    Good luck and hope all goes well.

    • Another question. Why do a lot of my worms move up into the lid of the compost bin? They crowd all up around the top and then when it gets too hot, they die! Why don’t they just migrate back down as I would have thought they would

      • Not to worry if it is only a few worms as it is quite normal. If it is a mass escape then see if your bin is too wet or too dry. Too much food going off. Too acid. Finely crushed sterilised eggshells or a sprinkle of dolomite powder will help neutralise the acidity.

  9. I lost all my worms one year when friends were looking after the house and the weather was hideously hot. Fortunately, there were heaps of eggs in the mix so I took out the eggs and put them in mixture in a polystyrene fruit box with holes in the bottom. I kept the eggs cool and shaded and soon had a whole new population of worms. I was thrilled to rescue my worm farm from extinction. So if you think you have lost your worms, have a look for eggs and you might not have to buy more worms. Worms are incredibly hardy. I can’t understand how people can kill their worms – they are the easiest animals I’ve ever looked after.

  10. I have a hungry bin style worm farm and came home yesterday after a 40 degree c day to about 50% of my worms liquefied. I think it was a combination of horse manure heating up and the heat itself. The worms at the bottom of the bin survived no problems. I wet the bin contents so its moist for today’s heat, covered with wet layers of newspaper and left the lid open so that the heat can escape. I have a feeling that ammonia gas from breaking down manure may of contributed as well. I have 2 hungry bins and 2 smaller bins and only my established main bin suffered. The others were ok. Lets hope today I come home to worms alive. I might try the ice block trick as western Sydney gets hot.

  11. Good luck Nadine, You will find the ice block method really effective. I have not had any dead worms since using the ice blocks Adelaide has not had any hot days yet but it will come sooner or later.

  12. 1.Use this opportunity to harvest a pot of worm wee for the garden.
    2.Run through another pot of water for tomorrow, this provides more cooling.
    3.Turn a plastic plant pot upside down, drape it with a sheet/hessian sack creating a ‘tent’.
    4.Place a half brick on top to stop the sheet blowing off, wet over the top preferably just before the sun comes around.

  13. Thanks David , I have put bamboo ticks vertically in , added a small plastic pot covered with a wet flannel , added a wet shedder blanket of paper. have I done enough ?
    I don’t what to loose anymore worms

    • I put a deep plastic tray on top of the lid, fill it with water then drape hessian sacks with the tops in the water – it wicks and keeps the outside cool – when it’s really hot I cover all that with a wet blanket.

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