How Temperature Really Affects Your Sourdough Fermentation

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Every sourdough baker eventually discovers that temperature is not just another variable, it is the invisible ingredient running the entire show. You can follow the same recipe, use the same flour, even mix at the same time of day, yet small temperature changes transform your dough into something that behaves completely differently. I learned this early on: a winter dough at 18°C barely moved for hours, while a summer dough at 25°C puffed up before I even finished cleaning the bowl. The difference was dramatic, and it taught me that fermentation responds to temperature more than almost anything else.

The organisms inside your starter, mainly wild yeasts and lactic acid bacteria, thrive in warm conditions and slow down when things get cooler. Their behaviour shapes everything from timing to flavour to dough strength. Warmer dough ferments faster and often produces a softer, milder loaf. Cooler dough ferments slowly, producing deeper acidity and building complexity. Understanding this balance is the heart of consistent sourdough baking.

Why Internal Dough Temperature Matters

Room temperature only tells part of the story. What matters most is the internal temperature of the dough itself. Dough can be cooler than the room if your flour and starter are cold, or warmer if you have used warm water or mixed vigorously. Once I started taking internal readings with an instant-read thermometer, my baking became dramatically more predictable. Suddenly I understood why the dough behaved differently from one bake to the next.

Internal dough temperature shapes the relative speed of yeast and bacteria. Yeast activity increases sharply as dough warms, creating gas and lift. Bacteria respond differently, producing acids that alter flavour and gluten structure. Your dough is most balanced between 24°C and 27°C (75–80°F). Below this, fermentation becomes slower and more forgiving. Above it, fermentation accelerates and can become harder to control.

Optimal Temperature Ranges

Professional bakers and serious hobbyists often target a dough temperature between 24°C and 27°C after mixing. This creates an ideal pace of fermentation, allowing gluten to strengthen and flavour to develop without racing ahead or lagging behind. Too cool and you wait all day. Too warm and the dough sprints toward its peak before it has developed structure.

Cold Dough

Cool dough around 18°C (64°F) ferments slowly, which can be helpful for flavour but unpredictable if you are not expecting it. I’ve made early-winter loaves that spent nearly two extra hours in bulk simply because the temperature dipped a few degrees. The dough eventually reached peak fermentation, but patience and gentle handling were essential.

Warm Dough

Warm dough at 26°C (79°F) or more can feel almost alive in your hands. It rises quickly, builds bubbles rapidly, and requires closer attention. One summer batch nearly doubled before I had finished my coffee. Using cooler water and fermenting in the lower part of the kitchen brought things back under control.

Measuring Internal Dough Temperature

An instant-read thermometer is one of the simplest tools that make a profound difference. Insert the probe into the centre of the dough right after mixing to determine your starting point. This number tells you how quickly fermentation will proceed. It also helps you adjust water temperature for the next bake: warm water for winter, cool water for summer.

How Temperature Feeds Into the Calculator

Your calculator uses internal dough temperature to estimate fermentation speed, adjusting the reference timing based on hydration, salt percentage, and inoculation. Higher hydration accelerates fermentation. Higher salt slows it down. More starter reduces bulk fermentation time, while less starter lengthens it. These adjustments create a dynamic prediction model far more accurate than any fixed-time recipe.

The Human Side of Fermentation

After years of baking, I’ve learned that dough teaches you as much as you teach it. You develop a feel for when the dough is relaxing, rising, strengthening, or slowing down. Temperature helps decode these signals. A dough at 22°C tells you to settle in for a long, flavourful bulk. A dough at 26°C urges you to stay nearby. A dough that feels cool, slightly resistant, and slow to rise behaves differently from one that feels warm, airy, and eager. These subtleties are what transform sourdough baking from a recipe-driven activity into a craft.

Controlling Dough Temperature

Fortunately, temperature is something you can influence. In winter, you can warm your water, use slightly warmer ingredients, or ferment the dough near a safe warm spot. In summer, you can reduce water temperature, choose a cooler area of the house, or retard part of the bulk in the fridge. Small adjustments make large differences in timing and flavour.

Summary

Temperature is the quiet force behind every successful sourdough loaf. By learning to measure internal dough temperature, adjust for seasonal shifts, and understand the behaviour of your dough, you unlock a new level of consistency and flavour. The more you notice and respond to temperature, the more your baking evolves from guesswork into intuition and skill.

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Frequently Asked Questions

What is bulk fermentation?

Bulk fermentation is the first rise after mixing, where dough develops flavour, gas, and structure.

Why does dough temperature matter?

Temperature directly controls fermentation speed. Warmer dough ferments faster, cooler dough ferments slower.

What is inoculation?

Inoculation is the percentage of flour coming from your starter relative to total flour in the dough. Higher inoculation speeds fermentation.

How accurate is the calculator?

The calculator provides an estimate based on proven fermentation models, but dough feel, strength, and volume should always confirm readiness.