Vermicomposting & Extreme Heat

Question from Barbara J.

Any word of the worms surviving 110 degrees heat? I live in Texas and wow
it is really hot.

Hi Barbara,

To be totally honest, it is very unlikely that any species of earthworm will survive being exposed to temps that high. As you get up towards (and past) 90 F even the most tolerant composting worms will tend to die off.

So, keeping a vermicomposting system going outdoors in 100+ F weather is incredibly challenging – and will only work if you can find ways to lower the temps inside the system.

Your chances of success will increase if you are using a system with excellent ventilation (and in a location with good air flow in general), and there is air flow within the habitat itself. They key will be to maintain moist conditions so as to take advantage of the evaporative-cooling effect. One interesting strategy I learned from my friend, George Mingin, involves draping a wet sheet over your system (again, the system itself needs to have excellent ventilation) and using a fan to blow air towards it.

If vermicomposting indoors really isn’t an possibility for you, another approach you might try is rotating frozen water bottles between your freezer and your system. This obviously has some limitations – especially if you are away from home a lot, but it does have the potential to be very effective! On a similar note – some might wonder about adding frozen food as a way to cool down a system. While this can indeed have some initial cooling effects, once the wastes thaw you could actually end up with the opposite effect. Accelerated microbial activity could lead to all manner of issues, such as excess heating and ammonia release.

One other potential possibility is some sort of in-ground system, especially if it can be positioned fairly deep in the ground – but, in all honesty, I’m not even sure if this would be a viable option when temps are getting up towards 110 F!

Anyway – hopefully this helps a bit.
Good luck!

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    • GA
    • August 22, 2013

    No experience with this particular issue (praise the lords, I’m no good in heat). But all geothermal heating/cooling systems work on one basic principle: at some depth, the temperature changes very little over the year. So I think digging to some depth – which might be as much as a meter or even more – and ensuring that the environment at that depth is ‘vermfriendly’ – should do the trick. They’ll just dig down and flee.
    In other words, dig an in-ground system and fill it with (loose) bedding and hopefully the worms will go there when they need to. Probably won’t be ideal but should let them surprise.

    • GA
    • August 22, 2013

    Whoops that should read ‘let them _survive_.’

  1. Not dissimilar problem. I mix my compost ‘bin’ with worms. I recently cut down and shredded a 40′ silver birch which I added to the compost. Over two or three days I noted the temperature rising to ‘hand hot’ or more. 5 dousings of water kept it moderate, but as with this reader, I fear for the worms when I eventually see them rise to the surface… if they do.

    • Steve
    • August 23, 2013

    With all the storm cellers I would think there would be someone that has developed an ideal below ground or ground covered environment. Maybe all those WWII era bunkers used by a variety of universities and businesses provide conditions condusive to worm farming. In fact all those survivalists with ventilated living space could provide ideal environments for worm production too.

    • Jimmy
    • August 25, 2013

    I think compost worms that have been given a chance to establish themselves in the soil before the summer arrives have a chance at surviving south Texas’ brutal summer heat. I say that because every time it rains here in San Antonio (zone 8b), I see Euros crawling up the the side of the house. I placed my 5 gallon bucket worm tower in the ground and put a 6 inch layer of shredded pallets (pine) mixed with compost around the outer circumference of the bucket (plus a layer of black bagged decomposing leaves). Keeping moisture in the soil helps also. Long story short, the worms are surviving the double wammy of intense drought and heat. African nightcrawlers in the summer/Euros in the winter.

    • JoAnn
    • September 4, 2013

    Here in SW Arizona it gets so hot and dry I wouldn’t dare keep my worms outside without building some kind of sunken worm bed with ultra insulated walls and a watering system and I don’t even know if that would keep them from getting too hot. I just started this project so I only have a couple worm bins that I keep under our kitchen table. One has a pound of red wigglers the other has maybe a half pound of European Nightcrawlers. I am thinking of getting African Night crawlers as they might be better suited for our climate.
    Our swamp cooler went down 3 weeks ago so our house gets as high as the 90’s inside. I put a probe in the soil in one of the bins and it gets up to about 78 to 81 so now every morning I have been laying a ice pack on top of the cardboard in the middle of the bin and put a piece of styrofoam on top of it. So if the worms feel too warm they can move towards it underneath. Every morning I swap the ice packs out with fresh ones. I haven’t lost any worms yet. It might not even be necessary but when the probe reads 80 degrees I get a little nervous. I hope this heat breaks soon, it has been a miserable summer with this humidity. Even my Ball Pythons are uncomfortable and they originated in Africa! :/
    JoAnn in Arizona

    • nom
    • September 17, 2013

    I have had an issue with heat. I am still in college, so housing is not ideal. I recently moved and kept my bin on the stairs to the basement (which we don’t have access to) and I discovered this area got pretty hot in recent weeks. I went to check on them one day and discovered they had all crawled through the gap between the lid and container and were committing mass genocide on the stairs! I quickly put them back into the container, punched more hole on the lid and changed locations until the temp. was cooler. Worms hate the heat.

  2. I beat this type of heat with a bin in the full sun in Ca. by placing open containers of water on top of the bedding and letting the lid open so that the breeze created an swamp cooler effect. The worms would gather under the containers. They survived and are thriving.

    • Texgal
    • January 25, 2014

    Does anyone know if the Worm Inn is a disadvantage during high heat? My plan is to keep it in the garage and I’m wondering if a plastic bin would be better to help retain moisture during the summer. The outside temp’s reach 100 during the summer so the garage is quite warm.

    • AD
    • July 25, 2015

    First thanks for all the great info!!!
    I would like to share my recent and new experience with vermicomposting here in Houston Texas. I work in the food business so I have a limitless supply of food scraps and cardboard to use. I recently decided to begin vermicomposting as the heat was already pushing the high eighties. My concern was spending time and money on a complex system only to watch things burn up so to speak. I did not want to wait until the fall as I am beginning to sow seeds for the second harvest of the year. To begin, I simply harvested red wigglers from my own soil, about 40 or so. After a couple of tweaks setting this up, I ended up digging a 12 in deep 20 in x 48 in rectangle in the ground. I tore up egg crate dividers and used shredded newspaper in the bottom to trap in moisture. I then placed about 4 inches of very rough un-sifted fresh compost. Now about two inches up from the actual soil level, I added my mixture of fresh “compost” or food. This was a mixture of fruit peels, lettuce etc and fresh mulch. I topped this with soil and water every three days. The pile is holding moisture nice and has already shrunk about 6 inches in three weeks. I feed it once a week with fresh nitrogen and carbon. I can find the worms feeding and breeding about 5 inches down from the top of the pile in outside temps of 95 degrees. Keep in mind this is now 6 inches above the soil level. With the limitations of the heat, I figured I would attempt a very simple system in case things don’t work out. I have already begun decomposing more food next to the pile so that in a month or so when the food has run out, they can move to the next pile and I can harvest the fertilized soil and fresh compost with minimal effort. The Pile is in full shade. It will be interesting to see if they are still in the pile next week as the heat indexes are pushing 110 degrees currently. I feel confident about it because I am using a local worm and the pile doesn’t seem to be very hot once I did down about 5-6 inches.

  3. Re Ad (#10). I would be concerned about rats
    with that ‘fresh’ food outside?

    • Bentley
    • August 7, 2015

    Apologies for missing some comments here

    Jimmy – it is VERY unlikely for Reds to become established in a typical soil, especially one in TX. They are adapted for life in organic-waste-rich environments.

    Bill – interesting strategy. Thanks for sharing!

    Texgal – the Worm Inn can definitely be challenging to work with outside in extreme heat, but I do know of at least one person who has had great success in a location that reaches 100+ F during summer.

    AD – Sounds like an interesting project, and I would tend to agree that a local composting worm (or at least one adapted for your local environment) is likely going to work much better than Red Worms (etc) you introduce.

    Dave – yes, I am following you around

  4. I smell an experiment. Bentleys compost heap+worms? 😉

    • Jim
    • June 17, 2022

    I have been watching the youtube of Arizona Worm Farm in Phoenix in which he runs a huge worm farm in the Hottest heat of az. None of his worm are underground. He does use a wedge method though with limited misting. Too much water conducts the heat. So search for him on You tube. He has over 12,000 people in the phoenix valley to whom he sells worms and compost. We moved from Phoenix Valley to a more temporate climate, but yesterday we had 107 temps and my worms did fine in an Urban Worm Bag. About once a day I do put in about 2 cups of Ice on the bag or on top of my bedding and it keeps every moist and cool. I have also put in four very small bottles of frozen water that are inside plastic bags and I have found that most of the castings occur around these bags of frozen water bottles.

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