Climate Impact on Sourdough Starters: What Bakers Must Know!

Sourdough starters are living ecosystems of yeast and lactic acid bacteria. Just as with any other living organism, their behavior, health, and vitality are greatly influenced by their environment. One of the primary environmental variables that can affect a sourdough starter is the ambient temperature and climatic conditions.

Climate significantly influences sourdough starter behavior. Warm, humid conditions accelerate fermentation, making the starter more active and possibly tangier. Conversely, cold climates slow down fermentation, requiring longer rise times and potentially yielding milder flavors. Keeping ambient temperatures consistent is key for predictable starter activity and bread results.

1. Temperature and Seasonal Changes

a. Hot Climates

In warmer climates or during the heat of summer, the yeast and bacteria in your sourdough starter become particularly vivacious. The warmer temperatures stimulate the microorganisms, causing them to become more active. As a consequence, the fermentation process speeds up considerably.

You’ll likely observe your starter expanding and doubling in volume at a much faster pace than in cooler conditions. This rapid growth is an indicator of the enthusiastic microbial activity happening within.

Because of the accelerated fermentation, the microorganisms consume their food sources more swiftly. To maintain a balanced and thriving starter, it’s crucial to feed it more regularly — perhaps every 12 hours, or in some cases, even more frequently. Regular feedings ensure the starter doesn’t become overly acidic, which can hinder its performance and influence the taste of your bread.

In such hot conditions, there’s a higher risk of overfermentation, which can make the starter too sour and weaken its rising power. Monitoring your starter for signs like a liquid layer on top or a particularly strong aroma can help you detect and address overfermentation early.

b. Cold Climates

As temperatures drop in colder climates or during the winter season, your sourdough starter will inevitably slow down. The cold suppresses the activity of the yeast and bacteria in the starter. This results in a more languid fermentation pace, making the starter appear less lively.

Unlike in hot conditions, your starter will take its time to rise and might not expand as much as you’re used to.

Due to the diminished microbial activity, the starter’s food consumption rate drops. Consequently, feedings can be spaced out further, potentially once every 24 hours or even less. It’s essential, however, to keep an eye on your starter’s health and adjust feeding frequencies based on its appearance and aroma.

Some bakers opt to store their starter in the refrigerator during colder months. This further reduces the activity but provides a consistent environment, elongating the time between feedings and offering a more controlled fermentation rate. When planning to bake, removing the starter from the fridge a day in advance and feeding it can reactivate and prepare it for use.

2. Humidity and Dryness

a. High Humidity

Regions with high humidity or seasonal spurts of moisture-rich air can present unique challenges and opportunities for sourdough enthusiasts.

High humidity can lead your starter to adopt a more liquid consistency. Flour has a hygroscopic nature, meaning it attracts and holds onto water molecules from the surrounding environment. Thus, in humid conditions, your starter might appear wetter than usual.

With extreme increase in hydration, the microbial activity can diminish, leading to slower fermentation rates. The yeast and bacteria in the starter struggle to function optimally when the culture is too thin and watery.

Given these changes, maintaining the starter’s balance becomes vital. Depending on your desired consistency and the specific flour you use, you might need to reduce the amount of water you add during feedings, opting for a stiffer starter, which can help counteract the excess moisture from the air.

b. Dry Climates

Contrastingly, dry climates, with their lack of moisture, can make sourdough starters behave quite differently.

As moisture evaporates more rapidly in dry climate, your starter might appear denser and thicker. The excessive loss of water can lead to a more paste-like consistency, which might not be as conducive for fermentation.

With extreme reduction in hydration, the microbial activity can diminish, leading to slower fermentation rates. The yeast and bacteria in the starter might struggle to function optimally without adequate moisture.

To counteract the drying effects, bakers might find it beneficial to slightly increase the water content during feedings. This adjustment can help maintain the desired consistency and promote healthier microbial activity.

To prevent excessive moisture loss, especially in extremely dry conditions, consider covering your starter with a damp cloth or placing it in a sealed container. This can help retain moisture and protect your starter from drying out.

3. Altitude Adjustments

Altitude has a profound effect on baking, and sourdough starters are no exception. When you’re baking in higher altitudes, there are unique considerations that can make the difference between a successful loaf and a baking mishap. Let’s delve into the intricacies of high-altitude sourdough baking.

a. Rapid Rise

One of the most immediate effects you’ll notice at high altitudes is how quickly dough rises. The lower atmospheric pressure allows gases (like carbon dioxide) produced during fermentation to expand more rapidly. This quicker expansion can lead to dough that rises faster and potentially overproofs if not monitored.

b. Addressing Hydration Concerns

Higher altitudes often come with cooler and drier air. This change in humidity can affect the moisture content of your starter and dough. In such conditions, your starter may lose moisture more quickly, leading to a denser consistency. To counteract this, consider increasing the hydration levels slightly. This means adding a bit more water than usual to maintain the desired consistency and ensure the health of the yeast and bacteria in your starter.

4. Protecting Your Sourdough Starter from Extreme Conditions

1. Temperature Regulation

a. Insulation Techniques

Your starter’s jar can be insulated against sudden temperature changes. Wrapping it in a thick cloth or towel provides a buffer. For extended protection, consider placing it inside an insulated cooler, which offers a more stable environment.

b. The Water Bath Approach

In fluctuating or particularly warm conditions, using a water bath can be advantageous. By placing your starter container in a water bath, the water evaporates and remains slightly cooler than room temperature, keeping your sourdough starter cool as well. You can maintain a more consistent fermentation temperature, safeguarding against overheating.

c. Strategic Refrigeration

When needing to slow fermentation—perhaps during a vacation or particularly cold spell—your fridge is your ally. This cools the starter, reducing microbial activity. Before baking, simply bring it to room temperature and proceed with regular feedings.

2. Adjusting Feeding Ratios

In warmer climates or during active fermentation periods, increase the feeding ratio. For example, instead of a 1:1:1 ratio of starter:water:flour, you could use a 1:2:2 ratio to provide more food for the active microbes.

3. Maintaining Consistency

To keep your starter’s consistency as desired, adjust the amount of water or flour during feedings, depending on ambient humidity or dryness.


Maintaining a sourdough starter is as much an art as it is a science. By understanding how environmental and climatic factors affect your starter, you can make informed adjustments to ensure it remains healthy and vibrant, no matter where you are or what the weather brings.


Hey there! I'm Sam, your go-to pal for all things sourdough. I've been baking and kneading for 10 fun-filled years, and I can't wait to share the joy of turning simple ingredients into heavenly sourdough bread with you. Grab your apron and let's dive into this amazing world of sourdough bread together on this blog.

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