It might feel like summer is behind us as the winds and rains of autumn sweep in. But cast your mind back to July, and you’ll likely recall just how hot this year has been. In the UK, temperatures this summer placed 2025 in the top 5% of all summers on record. Alongside the heat, we also experienced unusually high humidity.
As an island, the UK is naturally more humid than inland regions. However, with rising sea temperatures driven by warmer summers, the air masses moving over the country are now carrying more moisture than usual. This isn’t unique to the UK. In fact, global atmospheric water vapour levels reached record highs in 2024, with the average number of high-humidity days surpassing the previous record set in 2023 by 9.5 days.
So, what does this have to do with coffee?
When we talk about climate change, we often focus on how origin countries will be affected. But with temperature and humidity being two key factors in maintaining coffee quality during storage, ambient environments are becoming increasingly relevant to everyone in the supply chain.
Which makes now as good a time as any to revisit the age-old question: How should we store green coffee?
The link between temperature and specific humidity, Met Office
Who better to guide us on this topic than the experts in this field? We reached out to our suppliers in some of the world’s most humid countries to learn more about maintaining coffee quality in challenging environments.
Green Coffee Storage at Origin
Storing green coffee at origin presents a range of challenges, shaped by the environmental conditions of each producing country. High humidity and elevated temperatures are common, and these factors can significantly affect coffee quality—especially during its most fragile phase, from drying through to export. Managing moisture content in relation to ambient conditions is a delicate balancing act for producers and processors.
For many, this process begins on the drying patio. “We pick up coffee from patios around 9–10% to have a margin,” explains Andrés Salaverria, Managing Director at Jasal Coffee in El Salvador. “Once they are exported, they can be around 10.5–11%.” The climate becomes particularly challenging during the rainy season from May onwards, when temperatures hover around 30 °C and humidity can reach up to 86%. This period coincides with shipping, adding further complexity. “Humidity is our greatest challenge,” Salaverria continues. “If you don’t take into consideration Relative Humidity and this is too high, it can cause mould. If it’s too low, aging of the coffee is faster. For me, optimal drying and storage are really important to have good practices, as if not, coffee can easily and quickly be damaged.”
Washed coffees drying at Las Cruses Mill, Jasal
At Café Granja La Esperanza in Colombia, where innovative processing techniques are used to produce some of the world’s highest-quality coffees, moisture content in parchment is carefully maintained between 10% and 10.8%. Alexis Rodriguez, Quality Control Coordinator, highlights the risks: “One of the main risks is the moisture content in the parchment. If it is not within the proper range, mould development or the appearance of sensory defects may occur, such as pronounced woody notes, especially in the medium and long term.” He adds that controlling relative humidity and temperature is a major challenge, as their location experiences humidity levels between 70% and 85%, with an average temperature of 26 °C. Without proper control, these conditions can negatively affect the quality and long-term durability of the green coffee.
Bags stored in a humidity & temperature controlled room at CGLE
Once coffee is dried and stored in warehouses, factors such as temperature, humidity, ventilation, and exposure to sunlight all play a role in preserving quality. In Costa Rica, particularly in rainforest or coastal regions, humidity levels can be extremely high. For Coope Dota in the Tarrazú region, improper storage can lead to increased moisture and a range of defects. “If the coffee is stored improperly, there is a risk of increased moisture, as well as increase in defects according to the SCA standards, such as mould,” explains Walter José Godínez Garro. “Also, the risk of ochratoxin presence, accelerated aging of the coffee, loss of sensory qualities”, all of which can result in economic losses.
Coffee Bags at Dota
In Sumatra, the unique Gilling Basah processing method introduces additional complexity. Coffee grown and wet-hulled by the Permata Gayo Cooperative in Aceh is transported to Medan for final drying. Sama Aulia Saputra of the cooperative explains that while storage in Gayo is relatively safe due to synchronised humidity and temperature levels, Medan presents risks. “The temperature there is hot, so there’s concern that if not controlled, the coffee could become very dry.” Alongside mould, flavour degradation and insect control are key concerns. “If the water content is not controlled, it can cause the coffee to become mouldy or cause insect eggs in the coffee to hatch. If storage is not according to standards, it can change the taste of the coffee.”
Across all these origins, the common thread is clear: environmental conditions at origin—especially humidity and temperature—pose significant risks to coffee quality. Producers must carefully manage moisture content and storage practices to ensure that the coffee retains its sensory attributes and market value from drying through to export.
Stable temperatures and relative humidity (known as RH) are kept under tight control. “Storing coffee in spaces with relative humidity above 70% and temperatures higher than 23 °C, especially if there are significant fluctuations, can negatively affect quality over time,” suggests Rodriguez of Café Granja La Esperanza. As a result, the warehouses at Café Granja are constantly monitored for both relative humidity and ambient temperature, with a target range of 16–20 °C and 55%–65% RH.
Likewise, in El Salvador, Andrés and his team at Jasal maintain strict environmental controls. “The warehouse temperature ideally should be stable within 22–25 degrees Celsius. The relative humidity should be around 60%. Normally, most specialty coffee processed is stored in GP/Ecotact bags—this helps a lot in maintaining stable humidity and quality.”
Bag type, however, is not the only other consideration when storing green coffee. Good ventilation, adequate space, and cleanliness are also essential to ensuring the coffee remains fresh. Andrés explains how these factors contribute to good storage practices: “All coffee is piled up above pallets, so the coffee is never in contact with the warehouse floor. We avoid storing coffee close to machinery to prevent exposure to smoke or oil spills that can affect the final cup quality. We also try to be very cautious with the warehouse doors and avoid storing coffee close to them, as this coffee can be exposed to sunlight and higher temperatures. Finally, we leave 1.5 meters between the coffee stored and the warehouse walls to allow adequate space for ventilation, sampling, and mobility.”
How to Store Green Coffee
How should we apply this learning to a roastery environment? Here is a summary of the key considerations you should take when setting up or thinking about coffee storage in your roastery.
1. Temperature Control
Green coffee is sensitive to both temperature levels and fluctuations. Keeping temperature consistent is important to freshness.
Coffee should be stored in a cool environment between 15°C and 25°C. Anything above this can negatively affect quality over time, accelerate aging, leading to faded and papery or woody flavours. Very cold environments can also cause condensation when bags are opened, introducing moisture.
Best Practices:
- Store coffee in a temperature-controlled room or warehouse.
- Avoid placing coffee near heat sources like roasters or in direct sunlight.
- Monitor temperature regularly using digital thermometers or smart sensors.
2. Humidity
Humidity is arguably the most critical factor when storing coffee. Green coffee exposed to high ambient humidity can promote mold growth, while overly dry conditions can cause the beans to age quickly.
The optimum Relative Humidity for storing green coffee is 50–60%. Storing coffee above 70% RH risks mould growth.
Best Practices:
- Use dehumidifiers to maintain a stable RH.
- Measure relative humidity using a hygrometer.
- Use barriers such as GrainPro or Ecotact bags where possible.
3. Light Exposure
Green coffee should be stored in dark or dimly lit environments, as UV light can degrade green coffee, leading to accelerated aging.
Best Practices:
- Keep coffee in original packaging or store in opaque containers.
- Avoid placing coffee near windows or open doors in direct sunlight.
4. Airflow and Ventilation
Green coffee needs space to breathe. Ensure at least 30cm is kept between coffee stacks and walls, and keep coffee stored off the floor on pallets. Ensure there is a flow of air throughout the roastery space, especially towards the ceiling, where hot air can gather from the roasting machine.
Best Practices:
- Install fans or ventilation systems to ensure a steady recycling of air.
- Avoid storing coffee in ‘warm zones’, like near the ceiling.
5. Space & Stock Management
While temperature, humidity, light, and airflow are all important considerations, effective space management also plays a crucial role in preventing the degradation of green coffee. Implementing stock rotation, cleaning schedules, and Hazard Analysis Critical Control Points (HACCP) protocols can help reduce the risk of old stock, pests, or foreign substances compromising coffee quality
Best Practices:
- Rotate stock regularly using a first-in, first-out (FIFO) system.
- Ensure floors are kept clean and free of foreign matter.
- Maintain up-to-date HACCP and pest control protocols.
6. Monitoring and Quality Assurance
Coffee naturally evolves over time—sometimes for the better, sometimes for the worse. When stored properly, green coffee can remain fresh for 12 months or more. Vacuum-packed coffee may last even longer. Regular monitoring is essential to identify potential issues early and detect signs of ageing before they impact quality.
Establishing a weekly or monthly cupping schedule is an effective way to track changes in green coffee over time. Additionally, tools such as moisture and water activity meters can provide valuable data on internal changes within the beans.
Best Practices:
- Continue rotating stock using a FIFO system.
- Cup coffee regularly to monitor ageing and quality shifts.
- Consider ways to repurpose fading coffees (e.g as small components in espresso blends)
Good green coffee storage practices should be a priority for all roasteries, regardless of size.
By adhering to strict standards, roasters can preserve the integrity of the coffees they source, deliver exceptional quality to their customers, and gain deeper insight into the coffees within their roastery.
If you’d like to learn more about green coffee management or discuss your sourcing needs, get in touch with our team and subscribe to our newsletter. Whether you’re just starting out or are a seasoned professional, we’re always happy to share advice, connect you with origins, or help you make the most of your coffee.
