# Fermenting dosa batter in a cold kitchen

Source: https://howtomakedosa.com/ferment-dosa-batter-in-cold-weather/
Updated: 2026-09-25

In a 19 °C winter kitchen, dosa batter can sit for two days and barely move. It does not need a hot climate. It needs 26–32 °C for about 10 hours. Here are five ways to get that, with the temperature each one actually reaches.

## At a glance

| | |
|---|---|
| Target | 26–32 °C |
| Target | 79–90 °F |
| At target | 8–14 h |
| Stalls below | 18 °C |

## The number to aim for

Batter ferments well anywhere from **26 to 32 °C** (79–90 °F). Above 36 °C it turns sour before it rises. Below 18 °C it barely ferments at all.

| Where the batter sits | Typical temperature | Time to double |
|---|---:|---:|
| Winter kitchen counter | 17–20 °C / 63–68 °F | 26 h or more, often never |
| Heated living room | 21–23 °C / 70–73 °F | 18–24 h |
| Oven, light on | 27–32 °C / 81–90 °F | 9–12 h |
| Oven proof setting | 30–35 °C / 86–95 °F | 7–9 h |
| Instant Pot, Yogurt "Less" | about 30–32 °C / 86–90 °F | 7–9 h |

The temperatures for ovens and appliances vary by model. Put a cheap [probe thermometer](https://www.amazon.com/s?k=digital+probe+thermometer) next to the batter the first time, and write down what yours does.

## Five ways to get there

### Oven with the light on

The easiest, if your oven has an incandescent or halogen bulb. Put the batter in, switch on only the light, and close the door.

- Reaches: **27–32 °C** in most ovens after an hour
- LED oven lights: produce almost no heat, so this will not work
- Too warm (above 34 °C): leave the door open 2 cm with a wooden spoon

**Stick a note on the oven door:** Someone will preheat it with your batter inside. Tape a note to the handle.

### Oven proof setting

Many newer ovens have a "Proof" or "Dough proving" mode meant for bread. It usually holds about 30–35 °C (86–95 °F), which is at the warm end, so check at **7 hours**.

### Instant Pot, Yogurt mode

Put the batter in the steel insert and use the lowest yogurt setting ("Less" on most models). Keep the insert **no more than half full**, since the batter doubles. Use a glass lid or a plate in place of the sealing lid.

- Setting: **Yogurt, Less**, 8 hours
- Check at: **6 hours**
- The "Normal" yogurt setting runs close to 40 °C, too hot for batter

### Cooler with hot water

With no oven, put the batter inside a picnic cooler next to a 1-litre bottle filled with hot tap water, about 50 °C, and close the lid. The cooler holds about 28 °C for 6–8 hours. Refill the bottle once if you are going overnight.

### Warm the batter as you grind it

In winter the batter itself starts cold, especially if you soaked the grain in cold water. Grind with **room-temperature water** instead of ice water, aiming for a finished batter of **26–28 °C**. Keep it under 30 °C, so the grinder does not overheat the dal. The batter starts fermenting straight away instead of spending hours warming up.

## What else changes in winter

- **Soak longer:** 7 hours below 20 °C, instead of 5.
- **Salt after:** in a kitchen under 22 °C, stir the salt in after fermentation, not before.
- **Use a smaller vessel:** a half-full container holds warmth better than a large, mostly empty one.
- **Do not open it to check:** each look lets out warm air. Check through a glass lid, or at the times above.

### How do I ferment dosa batter in winter without an oven?

Put it in a closed picnic cooler next to a bottle of 50 °C water, or wrap the container in a thick towel and leave it on top of the fridge or near, not on, a radiator. Aim for 26–32 °C.

### Is it safe to leave dosa batter in the oven overnight?

Yes, with only the light on and the oven off. Tape a note to the door so nobody preheats it, and check the temperature first: it should stay under 34 °C.

### Can I ferment dosa batter in an Instant Pot?

Yes, on the Yogurt setting at its lowest level ("Less") for about 8 hours, with the pot at most half full and a glass lid on. Check at 6 hours.

### Why does my dosa batter ferment in summer but not in winter?

Temperature. The same batter that doubles in 8 hours at 32 °C (90 °F) can take 26 hours at 20 °C (68 °F), and may not rise at all below 18 °C.

## Keep going

- [Batter not fermenting](https://howtomakedosa.com/dosa-batter-not-fermenting/): The seven causes, most likely first, with a test for each and a way to save the batch.
- [Batter calculator](https://howtomakedosa.com/dosa-batter-calculator/): How many dosas, and how warm is your kitchen? Get every weight in grams and every wait in hours.
- [Idli](https://howtomakedosa.com/idli/): The same batter, not thinned, steamed for 10–12 minutes. What makes idli soft instead of dense.