Spring into Summer: How Rising Temperatures in the UK Affect Your Ferments

As we move from the gentle cool of spring into the warmth of early summer, kitchens across the UK begin to behave a little differently—especially if you’re someone who loves to ferment. Whether you’re nurturing a sourdough starter, brewing kombucha, or culturing kefir, the change in seasons brings noticeable shifts in how your ferments behave.

Here’s what you can expect as the mercury climbs—and how to keep your ferments happy in the warmer months.

🌡️ The Natural Rise in Temperature

Spring in the UK tends to hover between 10–16°C indoors, while summer can push indoor temperatures to the mid-20s or higher, especially during a sunny spell. That shift of 5–10°C might seem subtle, but in fermentation terms, it’s significant.

Most ferments are temperature-sensitive, and their behaviour can change dramatically as the warmth increases. Here’s a closer look at what happens to your favourite ferments as the days grow longer and hotter.

🍞 Sourdough Starter: Speedy and Hungry

In spring, your sourdough starter might take a solid 6–8 hours to double. As summer rolls in, that can shrink to 3–4 hours or even less.

What to watch for:

• Quicker rise times: Your starter and dough may be ready much sooner than expected.
• Overproofing risks: It’s easier to miss the sweet spot, especially if you leave dough out for too long.
• Milder flavour: Warmer temperatures favour lactic acid bacteria, which make your bread less tangy.

Tips: Consider using cooler water when mixing dough, feed your starter more frequently, or store it in the fridge between uses to slow it down.

🧉 Kombucha: From Slow Brew to Bubbly Brilliance

Kombucha brews sluggishly in the chill of spring but becomes much more active in early summer. The SCOBY loves temperatures between 24–28°C, which are more common indoors by June.

What changes:

• Faster fermentation: Your usual 10–14 day brew might be ready in 6–8 days.
• More fizz: Warmer conditions often lead to better carbonation in second fermentation.
• Tartness increases: Shorter brews are needed to avoid overly sour kombucha.

Tips: Start taste-testing your brew a few days earlier than usual, and bottle it before it becomes too acidic.

🥛 Milk Kefir: Fermenting Fast and Strong

Kefir grains ferment more quickly in summer warmth, often finishing in under 12 hours when it might take 24 in early spring.

What to expect:

• Separation: Warmer temperatures increase the chance of curds and whey forming.
• Stronger flavour: Kefir can taste more tangy or yeasty as fermentation speeds up.
• Grain growth: Your grains might grow faster, which is a good thing—up to a point!

Tips: Shorten your ferment time or move your jar to a cooler spot like a pantry. You can also refrigerate the finished kefir immediately to halt fermentation.

🧂 Sauerkraut and Vegetable Ferments: Bubbling to Life

Vegetable ferments like sauerkraut, kimchi, or pickled carrots become much more active in early summer. Expect more bubbles, quicker acidification, and potentially softer textures.

How to manage:

• Watch for overflow: Use a tray or fermentation weight to prevent spills.
• Brine levels: Keep an eye on evaporation and top up if needed.
• Shorten ferment times: Taste frequently; many ferments may be done in a week or less.

🌞 Final Thoughts: Embrace the Shift

The move from spring into summer is a joyful time in the UK, and it brings new energy to your ferments. While you’ll need to adjust your routines—checking your jars and crocks a bit more often—summer can yield faster, fizzier, and even more flavourful results.

With a bit of observation and flexibility, you’ll find this seasonal shift opens up new possibilities, whether it’s experimenting with shorter ferment times, exploring warmer-weather ferments like tepache, or just enjoying the fizz of a chilled bottle of kombucha on a warm afternoon.

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