Brazil's harvest was nearly complete by late August, adding to expectations of ample supplies. Consultancy Safras & Mercado reported that 97% of the country's harvest had been completed as of August 26, according to the report.
Brazil's National Supply Company, or CONAB, raised its estimate for the country's 2026 coffee crop to a record 67.6 million bags on September 24.
However, rain during the harvest affected bean quality, creating uneven availability across grades, the ICO said.
All coffee price indicators decline
All four group indicators tracked by the ICO fell in September, reflecting the broader weakness in the market.
Prices of Colombian Milds declined 8.1% from August to an average of 356.15 cents per pound. Other Milds fell 8.8% to 329.44 cents per pound, while Brazilian Naturals dropped 9.9% to 290.19 cents per pound.
Robusta prices fell 7.3% to 167.49 cents per pound during the month.
The price difference between Colombian Milds and Other Milds widened 2.1% month-on-month to 26.71 cents per pound in September.
Meanwhile, the arbitrage between the London and New York futures markets narrowed 13.2% to 126.40 cents per pound, the report showed.
Global coffee exports rise 14.6% in August
Global green coffee bean exports rose 15.6% year-on-year to 10.94 million bags in August, compared with 9.46 million bags a year earlier.
Exports increased across all coffee groups except Colombian Milds. Robusta shipments rose 22.4% from a year earlier to 4.36 million bags, while Brazilian Naturals exports increased 21.3% to 3.57 million bags.
Exports of Colombian Milds declined 5.6% year-on-year to 1.09 million bags. Each bag weighs 60 kg.
Including all forms of coffee, global exports increased 14.6% year-on-year to 12.55 million bags in August.
Coffee exports showed mixed trends across regions in August, with Asia and Oceania and South America recording strong growth.
Shipments from Asia and Oceania rose 23.1% year-on-year to 4.03 million bags. South America's exports increased 20.2% to 5.98 million bags.
In contrast, exports from Africa fell 1.8% to 1.74 million bags. Shipments from the Caribbean, Mexico and Central America declined 14.3% to 790,000 bags.
Global coffee market set for surplus
The ICO expects global coffee production to rise 4.4% to 183.6 million bags in the 2025-26 coffee year, which runs from October to September.
Global consumption, meanwhile, is projected to decline 0.8% to 180.6 million bags.
Based on these estimates, the organisation expects a global coffee surplus of 3 million bags in the 2025-26 coffee year. This would follow four consecutive years in which the market recorded deficits.