How to Warm a Sourdough Starter

Warming a sourdough starter is essential to kick-starting fermentation activity. A sourdough starter needs warmth to allow the yeast and bacteria to ferment the flour. If you don’t already have a sourdough starter, you can use my sourdough starter recipe.

The ideal temperature for sourdough fermentation is 25-35C (77-95F) whilst a temperature above 20C (68F) shouldn’t cause too much of a problem, it’ll be slow to rise.

Many bakers in cooler climates struggle to get their starters to rise. There isn’t a “best way to warm a starter”, there are several methods that you can choose from that won’t require you to move closer to the equator. You can also use these tricks to warm your proofing sourdough bread too.

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Warm your starter with the oven proof setting

Some ovens have a bread proof setting on them, they are usually set around 30-35C (86-95F) which is perfect. Using this method will mean you will have to feed twice a day. It might be too warm for bread made with a long bulk fermentation so keep an eye on the dough so it doesn’t over ferment.

Use the oven or microwave light to warm the starter

Placing the starter on a tray in the microwave or oven with the light on is enough warmth to keep the starter active. You might have to be a bit creative to keep the door close on the microwave without the light turning off, otherwise this is quite a solid way to allow your starter and your bread to ferment.

Place the starter on top of the oven

I often put my dough to its final rise on top of the oven. It warms it up just enough to speed up the rise. You can do the same with your starter but it’s only going to be a temporary fix whilst the oven is in use.

Warm the starter on the window sill

Have the sun warm it up. It works surprisingly well however some bakers find that the sunlight damages the starter so don’t use a transparent container.

Use warm water when refreshing your starter

Using warmer water will help kick start the activity. Though it won’t last forever, in cooler environments it can give your starter or bread a nudge in the right direction.

Use a deicated proofer to warm the starter

Although costly and hard to get hold of a proofer offers the most consistent temperature and humidity levels with the least amount of worry. Pop your starter in, set the temperature and off you go. No need to panic!

Here’s the only one I can find that doesn’t cost thousands. At the moment it’s not available in every country so you’re lucky if you can get one. Fantastic reviews too!

Brod and Taylor home proofer

View the latest price at Brod & Taylor or see Amazon

Make a DIY proofer for your starter

It can be tempting to build your own proofing box so save your pennies, and I tried it and it works really well! The insulating mats I used were fairly cheap and the running costs are very low.

Here’s how to make a DIY proofing box.

Put your starter in the airing cupboard

Not every home has an airing cupboard but those that have space around your boiler can use it to warm a starter.

Use a yoghurt maker to store your starter

It might sound silly but I found a secondhand yoghurt maker for around $15 and it’s awesome! I can set the temperature accurately to make the perfect environment for my happy starter!


There are many solutions to the problem which depend on how much warming you have to do and what you already have around you. Buying a proofing box is the most reliable way. Though you can use the other techniques to get an occasional boost.

If you’re just starting out in your sourdough journey, check out my sourdough bread recipe for beginners. It breaks everything down into simple steps and should help you to make fantastic bread.

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  1. I cooked my yogurt in a small cooler wrapped in towels. I have also used the insulated box that meal subscriptions come in. I works for my starter too.

  2. I started one week ago. The first few feeds my starter doubled and i could ear gas. Now it no longer rises and sound of gas when i open the jar. With the feed the jar is almost full. I can still see bubbles. I tried to make bread but the dough was sticky and i was unable to shape it and it did not look risen to me. Not sure what i am doing wrong. It is autimn now in south africa and nights can be a little chilly

  3. Not a lot, you probably just need to warm it up! Starters are always vibrant in the first few days, but this drops off as it becomes more alcoholic and acidic. This means that different strains of yeast and bacteria need to multiply and replace the ones utilised in the starter’s early days. It’s perfectly normal for a new starter to behave like this. Try and put it in a warmer place, keep feeding at least daily and it should come good in a couple of weeks.

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