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How to Keep Your Jars Warm In Cold Seasons

Updated: Oct 28, 2021

A lot people want to know how to keep their grain jars warm during the winter months.

The best way is to increase the ambient air temperature to 78-80 degrees Fahrenheit. However, this can sometimes be costly if you’re running your heater for your entire house just to keep these jars warm. And really, it’s just unsustainable.

You may have heard that you can use seed tray warmers or pet bed warmers, but I’ve used these methods with disastrous results.

The direct heat to the jars can hinder mycelial growth or kill it. I once used a seed warmer and baked my grains into oatmeal. So, if you go this route, use extreme caution.

Alternative to heating your whole house or using seed tray warmers

Try increasing the ambient air temperature by using a hot water bottle and an ice chest. A lot of people already have these kinds of things laying around their house. Hopefully you do too.


  1. Fill a hot water bottle with some hot water. Start at 115 degrees Fahrenheit water. This "hot" on your kitchen sink.

  2. Place the hot water bottle and jars inside an ice chest

    1. Cooler should be large enough for space between bottle and jars

  3. Monitor and adjust

Optimal temperature is 78 degrees. However, this cooler method requires that you change water periodically. Depending on your quality of insulation, you may have to change the water every couple days. The better insulation, the fewer times you have to change the water.

Video Tutorial

Monitoring temperature

You might also want to consider getting a Wi-Fi Thermometer. This one by Govee is pretty great and not too expensive. It syncs over wi-fi, which is good because it can give you historical data about the temperature and humidity levels inside your house. You can download the data anytime you want. This thing gives a really cool insight into your home environment.

It syncs over wi-fi and displays the information on your phone through their app.

Highly recommend it! You can also get it from Amazon.

The Govee thermometer helps by:

  1. Making sure the inside of the cooler isn’t too hot.

  2. Making sure the inside of the cooler isn’t too cold.

  3. Let’s you know, at glance, when you need to change your water.

If you've got any questions, drop 'em in the comments below! Or message me on WhatsApp!

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