Temperature Control Is the Secret to Perfect Sourdough

Today, we’re excited to bring you a guest post by an absolute expert in the world of sourdough, Parker Cook of Bail and Bloom. Read on and see what Parker has to say about the importance of temperature in baking sourdough bread!

Most sourdough bakers have had that moment—pulling back the lid on a batch of dough and wondering, Why does this feel different than the last time? It’s the same recipe. The same timing. And a totally different result.

More often than not, the missing variable is temperature.

While it’s easy to focus on flour, hydration, and timing, dough temperature (and your kitchen’s ambient temperature) during bulk fermentation quietly shape the outcome of your sourdough bread—from rise and texture to flavor.

If you’re not paying attention to your dough’s temperature, you’re missing a secret ingredient. The knowledge you get from an instant-read thermometer like Thermapen® ONE helps you troubleshoot so many aspects of your bread baking.

Thermapen ONE

Understanding Bulk Fermentation

Bulk fermentation—the period between mixing your dough and shaping your loaves—is where your sourdough starter does the real work.

The yeast and bacteria from your starter consume nutrients from the flour and multiply. During this process, two key things happen:

Yeast produce carbon dioxide gas, creating bubbles and giving your dough its rise.
Bacteria produce acids, contributing to sourdough’s signature flavor.

Temperature is a key driver of both of these functions. Microbial activity slows in cooler dough and speeds up in warmer dough—something bakers can use to their advantage and manipulate to meet their goals, especially with the help of an accurate thermometer like Thermapen ONE.

How Dough Temperature Affects Bake Time and Flavor

Whether you’re a night owl or an early riser, your dough’s temperature will determine when—and how well—your sourdough turns out.

One baker may enjoy a hands-off approach to bulk fermentation, mixing dough in the evening and letting it ferment overnight. Meanwhile, another baker might start a batch first thing in the morning, aiming to serve fresh bread by lunchtime.

Assuming both bakers are using an equally strong starter, here’s how temperature comes into play:

A cooler dough temperature (65–68°F) allows for longer fermentation overnight, minimizing the risk of overproofing (which leads to gluten breakdown and structure loss). If you struggle to cool down your dough, whether that be from living in a warm environment or from mixing by machine (which adds heat via friction), you can refrigerate your water before adding, or even add water in the form of ice cubes. (With a mixer you can add the ice cubes directly; if mixing by hand you can chill the water with ice, but avoid adding ice directly as it will be difficult to mix in by hand.)
A warmer dough temperature (80°F+) speeds fermentation, allowing bread to be ready in as little as 5–6 hours—ideal if you’re skipping cold proofing. (If your home sits at around 68°F like mine, and you want to keep your dough above 80°F for faster fermentation, turn on your oven light and place your dough inside the oven. Most ovens with just the light on maintain a dough-friendly temperature above 80°F—an affordable, reliable solution that works year-round.)

If the overnight baker keeps their dough above 80°F, they’ll wake up to a puddle of structureless goop. Meanwhile, if the morning baker ferments below 70°F, they might not be shaping until well after dinner.

While temperature impacts fermentation time, it also affects flavor:

Cooler dough = longer fermentation = more acid = a tangier loaf
Warmer dough = faster fermentation = less acid = a milder, wheat-forward flavor

Although “sourdough” implies sourness, with some experimentation you may find—as I have—that you prefer a balanced loaf with mild tang that lets the flavor of the grain shine.

Better Temp Tracking, Faster Fermentation

At Basil & Bloom, I bake for our local farmer’s market, regularly producing 150+ loaves per weekend on my own. At the time of writing, I can only mix 10 loaves at a time, which means my dough days are long.

If I followed standard temperature guidelines (typically 73–77°F), each batch would take 4–6 hours to ferment, which would drag my production into the night. Instead, I do two things:

Target a dough temperature of 83–85°F, measured using ThermoWorks Thermapen ONE™ and monitored/maintained using RFX™ Wireless Probes by ThermoWorks.
- The Thermapen ONE’s measurement speed allows me to quickly make a decision whether I need to warm or chill my dough to meet my needs, while the continuous monitoring by the RFX helps me keep a record of each batch as well as make micro adjustments to maintain my desired dough temperature.
Increase the percentage of prefermented flour (a measurement of the flour contributed to your dough by your sourdough starter) in my formulas.

This lets me complete each batch’s fermentation in as little as 2.5 hours—a massive difference in workflow.

When Should You Use a Thermometer?

More often than you think! Temperature isn’t just something you monitor while baking—tracking it throughout your process gives you better control and consistency.

With the right tools, temperature tracking becomes second nature. Here’s how I recommend using ThermoWorks gear:

SPOT™: I stick this handy, magnetized thermometer to my shelves to continuously monitor my kitchen’s ambient temperature. This helps me better anticipate how long my dough needs to ferment.
Thermapen® ONE: I use this crowd-favorite thermometer to check my water temperature before mixing, and to verify my final dough temp after mixing. It’s super accurate and reads in just one second.
RFX™ Wireless Probe: This hands-free tool helps me monitor dough temperature throughout bulk fermentation. The wireless probe sends data to the cloud, so I can get instant updates from anywhere via the app. And the data logging feature allows me to compare different bakes for consistency.

Temperature isn’t just a background detail in sourdough baking—it’s a primary tool for shaping, fermentation, flavor, and workflow. Whether you’re baking a couple of loaves for your family or producing hundreds for a market, consistently monitoring and adjusting dough temperature gives you more control, better results, and fewer surprises. With the right tools and a bit of attention, you can make temperature work for you—not against you—in every bake.