The Best Temperature for Proofing Dough at Home (and How to Get It)

Temperature is the variable that quietly controls everything in sourdough, and it's the one most home bakers never measure. Two people following the same recipe in kitchens eight degrees apart are running completely different processes.

The target

24–26°C for bulk fermentation. That's the range most recipes silently assume, and the range where published timings actually work.

Here's what happens outside it:

• Below 18°C: fermentation nearly stalls. A four-hour bulk becomes ten or twelve.
• 18–21°C: slow. Roughly double the recipe's stated time. Common in European kitchens outside summer.
• 22–26°C: the target. Recipe timings roughly apply.
• 27–30°C: fast. Recipe timings are wrong in the other direction — you can overferment in three hours.
• Above 30°C: bacteria outpace yeast. Sour, slack dough that spreads.

A rough working rule: every 1°C of change alters fermentation speed by around 5–10%. Four degrees is not a detail.

Your kitchen is colder than it feels

A kitchen that feels comfortable is often 19–20°C. Worse, dough sitting on a stone or tiled counter is colder than the air — sometimes by two or three degrees, because the counter conducts heat away.

This single fact explains most "I followed the recipe exactly and it didn't rise" experiences. Put a cheap thermometer next to the dough, not on the wall, and check it at the level the dough sits.

Six free ways to make a warm spot

1. Oven with the light on. The bulb usually holds an oven around 25–28°C. Check yours — some run hotter. Leave the door slightly ajar if so, and put a note on the oven so nobody preheats it with your dough inside. This has happened to everyone once.
2. Oven with a bowl of hot water. No light? Put a bowl of just-boiled water on the bottom shelf, dough on the shelf above, door closed. Refresh every couple of hours.
3. On top of the fridge. The warmest surface in most kitchens, usually two to four degrees above room temperature.
4. A cool bag. Insulated bag, dough inside, jar of warm water beside it. Cheap, portable and surprisingly stable.
5. Near a radiator — carefully. Not on it. A metre away, on a chair. Direct heat cooks the outside of the dough.
6. Adjust the water instead. Warmer mixing water raises the dough's starting temperature. This is what professional bakeries do — they calculate water temperature to hit a target dough temperature.

Cooling things down in summer

Summer overfermentation is more common than people expect and produces slack, sour, sticky dough.

Use cold water from the fridge for mixing, use less starter — dropping from 20% to 10% roughly halves the pace — and put the dough in the fridge for the last part of the bulk. A cellar or the coolest room in the flat works too.

Cold proving is a technique, not a compromise

The overnight fridge prove exists for two reasons beyond convenience.

First, flavour: at 4–6°C the yeast slows dramatically but the bacteria producing acids keep working, so a cold prove develops complexity that a warm one can't.

Second, handling: cold dough is firm and much easier to score cleanly, which is the main reason cold-proved loaves get better ears. See how to score sourdough.

Eight to sixteen hours in the fridge is the useful range. Bake straight from cold — no need to bring it back to room temperature.

Stop timing, start reading

The real lesson of temperature is that clock times in recipes are approximations of somebody else's kitchen. The dough tells you where it is: risen 50–75%, domed, airy, bubbles at the edges of the container.

Use a straight-sided clear container so you can see the rise as a percentage rather than guess it. It's the second-best purchase after a thermometer.

Once you're recording temperature alongside timing, patterns appear fast — you'll know your own kitchen's winter and summer schedules within a month. That's most of what a baking notebook is for.

Questions we get asked

What temperature should sourdough proof at?

24–26°C for bulk fermentation, which is what most recipe timings assume. Cooler works fine but takes considerably longer; above 30°C the balance shifts towards sourness and slack dough.

How do I proof dough in a cold kitchen?

Oven with the light on, or with a bowl of just-boiled water inside. Failing that, on top of the fridge, or in a cool bag with a jar of warm water. Warmer mixing water also raises the starting temperature.

Can I proof dough in the fridge overnight?

Yes, and it's worth doing. Eight to sixteen hours at 4–6°C builds flavour and makes the dough much easier to score. Bake straight from cold.

How much does temperature change fermentation time?

Roughly 5–10% per degree. A dough that bulks in four hours at 25°C can easily need eight or more at 19°C — which is why following the clock instead of the dough goes wrong.