Your kitchen hits 28°C (82°F) and suddenly the bulk ferment you nailed all winter turns into a slack, over-proofed puddle by the time you go to shape it. This is the summer sourdough problem, and almost every home baker runs into it once the seasons shift.
The fix isn't complicated, but it means letting go of the rigid recipe times you've been following. In summer, the dough sets the pace, not the clock.
Why summer changes everything
Fermentation speed rises sharply with temperature. A practical rule that matches the calculator on this page and the rest of this site: rate roughly multiplies by 2.2x for every 8°C (14°F) increase in dough temperature, within the range we care about. So a dough at 26°C (79°F) ferments noticeably faster than one at 22°C (72°F), and at 28°C (82°F) it's flying. Lactic acid bacteria shift too: warmer doughs tend to push more lactic acid the longer fermentation drags on, which changes flavor as well as timing.
Two things go wrong in summer:
- Bulk fermentation overshoots. You follow a 5-hour bulk that worked in March, and by hour 3 the dough is already 90% risen, gassy, and sliding off the bench scraper.
- The dough heats up during bulk. Mixing generates friction. A warm kitchen heats the dough further. By the end of bulk, dough that started at 24°C (75°F) can be 28°C (82°F) or more, and the last hour ferments at the fastest rate of all.
Both problems compound. The result is over-proofed dough that turns into a flat, sour, gummy loaf. (If the flat-and-gummy part is your recurring failure, see why sourdough turns out gummy.)
The single most important number: dough temperature
If you don't already track desired dough temperature (DDT), summer is when you start. Many sourdough recipes quietly assume a DDT around 24–26°C (75–79°F). In a hot kitchen, you have to actively cool your inputs to hit that.
The water-temperature formula, the same one used in the DDT guide, is:
Water temp = (DDT × 3) − flour temp − room temp − friction factor
The multiplier is 3 because three temperatures are subtracted (flour, room, friction); the levain is treated as roughly room temperature. Friction is about 2–3°C for hand mixing and 5–8°C for a stand mixer.
Worked example, hand-mixed: kitchen 28°C (82°F), flour 28°C (82°F), DDT 24°C (75°F), friction 2°C.
Water = (24 × 3) − 28 − 28 − 2 = 72 − 58 = 14°C (57°F).
That's already cold tap-water territory. Now push the kitchen to 30°C (86°F) with warm flour to match: (24 × 3) − 30 − 30 − 2 = 10°C (50°F), or 9°C (48°F) with 3°C of friction. That's colder than most summer tap water, so you're into ice. Mix with a stand mixer (8°C friction) and it drops to 4°C (39°F); at 32°C (90°F) it hits 0°C (32°F), the limit of what liquid water can do. That's the real summer lesson: in a hot kitchen, water temperature alone runs out of room fast. You have to chill the flour, use ice as part of the water weight, or accept a higher DDT and shorten bulk hard.
Practical ways to cool your inputs
- Refrigerate the flour. A bag in the fridge overnight can drop more than 10°C, which moves your required water temperature up into pourable range.
- Use ice water. Weigh the ice as part of your hydration total. For example, 50 g ice plus 300 g cold water gives you 350 g of water for the recipe.
- Use a cool levain. A levain pulled straight from peak at room temperature is warm and active. Some bakers build it earlier and chill it for 20–30 minutes before mixing.
- Mix in a cool spot. Stone or granite counters pull heat out of the bowl better than wood or laminate.
Adjusting bulk fermentation for heat
Forget "bulk for 4–5 hours." Watch the dough.
Here are realistic bulk times at common dough temperatures, assuming roughly 20% levain built from a healthy starter. These follow the canonical curve (about 5 hours at 24°C, scaling 2.2x per 8°C) used across this site and in bulk fermentation by temperature:
| Dough temp | Approx. bulk time | Watch for |
|---|---|---|
| 22°C (72°F) | ~6 hours | 50–75% rise, smooth top, jiggly |
| 24°C (75°F) | ~5 hours | 50–75% rise, domed, bubbles on sides |
| 26°C (79°F) | 3.5–4.5 hours | About 50% rise |
| 28°C (82°F) | 3–3.5 hours | About 50% rise, faster surface bubbles |
| 30°C (86°F) | ~2.75 hours | About 50% rise; check every 20 minutes |
The hotter the dough, the closer to the low end of the usual 50–75% rise you want to shape. That sounds backwards, but warm dough keeps fermenting aggressively after you shape it, through the proof, and even into the early bake. You're banking on residual activity, so you pull it earlier.
Signs of bulk completion in hot weather
- Dough has risen about 50% from when the salt went in (the low end of the usual 50–75%)
- Surface is domed and shiny, not flat
- Visible bubbles on the sides of the container
- Jiggles like set custard when you nudge it
- Pulls away cleanly from the container wall
If you see large surface bubbles that have already popped, or the dough looks slack and webby, you're past the window. Shape immediately and get it into the fridge.
How much to cut the levain or chill the water
There are two levers for pulling a hot-kitchen bulk back to a plannable length: less levain, or a cooler dough. The numbers below are predictions from the fermentation model behind the schedule calculator (5 hours at 24°C with 20% levain, 2.2x faster per 8°C warmer, and about a third longer with half the levain, as in published test bakes). Treat them as estimates to plan around; the dough still has the final say.
Predicted bulk time at a steady dough temperature:
| Dough temp | 10% levain | 15% levain | 20% levain |
|---|---|---|---|
| 26°C (79°F) | 5.4 h | 4.6 h | 4.1 h |
| 28°C (82°F) | 4.4 h | 3.8 h | 3.4 h |
| 30°C (86°F) | 3.7 h | 3.1 h | 2.8 h |
| 32°C (90°F) | 3.0 h | 2.5 h | 2.3 h |
To get back to about 5 hours with levain alone, the model points to roughly 12% at 26°C and 7% at 28°C, which is already below 10%, where the model extrapolates. From 28°C up, less levain on its own is not a practical fix: chill the water as well. In the model, the same limit makes an overnight bulk on the counter impractical in a warm kitchen; overnight bulk fermentation shows where it still works.
Water temperature to hold a 25–26°C (77–79°F) dough (hand mix, 2°C friction, flour at kitchen temperature):
| Kitchen and flour | Water for 25°C (77°F) DDT | Water for 26°C (79°F) DDT |
|---|---|---|
| 26°C (79°F) | 21°C (70°F) | 24°C (75°F) |
| 28°C (82°F) | 17°C (63°F) | 20°C (68°F) |
| 30°C (86°F) | 13°C (55°F) | 16°C (61°F) |
| 32°C (90°F) | 9°C (48°F) | 12°C (54°F) |
Combine the two and a 5-hour bulk comes back within reach: the model puts a 25°C dough with 15% levain at about 5.1 hours, and a 26°C dough with 12% levain at about 5.0. A stand mixer adds roughly 3–6°C more friction than hand mixing, so take that off the water as well. The calculator runs this arithmetic for your own kitchen, flour and levain numbers.
Cold retard: your summer best friend
A cold retard (overnight in the fridge after shaping) slows fermentation to a manageable rate and firms the dough so scoring works. In summer the move is simple: shape earlier than you think and retard longer. A 12–16 hour cold proof at about 4°C (39°F) buys you flavor without over-proofing.
If your fridge runs warm, above 6°C (43°F), your retard isn't really retarding. A cheap fridge thermometer settles the question. For when to lean on retarding versus a same-day bake, the trade-offs live in cold retard vs same-day.
Hydration: dial it back
If you normally bake at 78% hydration, drop to 72–75% in summer. Two reasons:
- Warm dough is structurally weaker: gluten softens at higher temperatures, so the dough holds shape worse.
- Faster fermentation means more enzymatic activity, which degrades gluten further.
A slightly stiffer dough gives you a margin of error. You can push hydration back up in October. The full mechanics are in hydration explained.
Starter management when it's hot
Your starter is in the same hot kitchen. It will peak fast, sometimes in 3–4 hours instead of 6–8, and collapse before you're ready to mix.
- Feed at looser ratios. A 1:5:5 or 1:10:10 feed (starter:flour:water) takes longer to peak, which buys you scheduling room. The mechanics are in starter feeding ratios.
- Use cool water for feeds. Around 16–18°C (61–64°F) slows things down.
- Build the levain on a timer. If you want to mix at 9 a.m., work backward: in a 28°C (82°F) room a 1:5:5 levain peaks in about 5 hours by the model, so a 9 a.m. mix means building it at about 4 a.m. Easier: use a looser ratio, or mix at noon as in the timeline below.
- Keep the mother in the fridge between bakes and only build levains for active baking. It works year-round, and it pays off doubly in summer. In July, keep the jar at the back of the fridge and only wake it the day before a bake; a starter left on the counter in summer heat runs past its peak again and again.
Shaping and scoring a warm dough
Warm dough is slack dough. Three adjustments:
- Use a little more bench flour during shaping than you would in winter. Light, but use it.
- Pre-shape, rest 15–20 minutes, then final shape. The rest lets surface tension build. Skipping pre-shape works in winter but often fails in summer. For the grip technique, see the stretch and fold guide.
- Score it cold. Warm dough drags on the lame and tears. A loaf that's been in the fridge 8+ hours scores cleanly; see scoring sourdough.
A summer-adjusted timeline
A workable schedule for a kitchen running 28°C (82°F):
| Time | Step |
|---|---|
| 7:00 a.m. | Feed levain 1:5:5 with 16°C (61°F) water |
| 12:00 p.m. | Levain peaks; mix dough with ice water targeting 24°C (75°F) DDT |
| 12:30 p.m. | Stretch and fold #1 |
| 1:00 p.m. | Stretch and fold #2 |
| 1:30 p.m. | Stretch and fold #3 |
| 2:00 p.m. | Stretch and fold #4 (a coil fold if the dough is slack) |
| About 4:00 p.m. | Bulk complete at about 50% rise (the model's estimate is about 4 hours); pre-shape |
| 4:20 p.m. | Final shape, into a covered banneton |
| 4:30 p.m. | Into the fridge at about 4°C (39°F) |
| Next morning, 6:00 a.m. | Preheat the oven to 250°C (480°F) for 60 minutes |
| 7:00 a.m. | Bake straight from the fridge; cool at least 1 hour before slicing |
The model puts this bulk at about 4 hours for a 24°C (75°F) dough warming in a 28°C (82°F) kitchen (20% levain). Check from hour 3, because a dough that runs warmer than planned finishes sooner. In an 18°C (64°F) winter kitchen, the same flour and starter would need about 9 hours by the calculator's model (9.0 h at 20% levain); see winter sourdough for the cold-kitchen mirror image. Same dough, different season.
Common questions
How do I know if my dough is over-proofed before I bake it?
Use the poke test: lightly flour a finger and press about 1 cm into the dough. If it springs back fully, it's under-proofed. If it springs back slowly and leaves a slight dent, it's ready. If it doesn't spring back at all, or the dough deflates, it's over-proofed. In summer an over-proofed dough often also looks visibly bubbly on the surface and feels almost liquid underneath. The poke test's blind spots, especially on cold dough straight from the fridge, are covered in the troubleshooting guide.
Can I just bulk ferment in the fridge in summer?
Not on its own. A pure cold bulk is slow and tends to produce sour, dense loaves with tight crumb, because yeast slows down faster than the bacteria do. A better approach: 1–2 hours of warm bulk to get fermentation moving, then move the container to the fridge for 8–12 hours, then shape cold and proof in the fridge.
My starter doubles in 3 hours now. Is that bad?
No. That's normal for warm temperatures and means it's healthy. But it changes how you build levains. Don't feed a starter, walk away for 8 hours, and expect to use it at peak. Feed looser ratios (1:10:10), use cool water, or refrigerate it once it peaks.
Should I change my flour blend in summer?
A bump in whole grain (5–10% more whole wheat or rye) ferments faster, which works against you when speed is already the problem. Lean a bit more on bread and white flour blends in summer for better gluten structure in warm conditions, and save the whole-grain experiments for spring and fall (whole wheat sourdough).
Why does my summer crumb look tight even though the dough seemed well-proofed?
Usually because the dough over-proofed during bulk, lost its gas structure, and then couldn't recover in the bake. Counterintuitively, tight, gummy crumb in summer is often an over-proofing problem, not under-proofing. Shorten your bulk by 30–45 minutes next time, and if dense loaves are a pattern, see fixing dense sourdough.
Do I need a proofing box or special equipment?
No. Most summer issues are solved with a thermometer, ice, and a willingness to ignore the recipe clock. A proofing box matters far more in winter, when you need to add heat, than in summer, when you're trying to remove it.
Summer in four moves
Pre-chill the flour, weigh ice into the water, shape at about 50% rise rather than the top of the range, and retard overnight at about 4°C (39°F).