On 3 September, a number that moves billions of dollars of cargo will quietly shrink by two: the Panama Canal Authority announced that the daily vessel quota will fall from 36 to 34 ships, and then to 32 by 15 September. The cause is a rainfall deficit that has stripped the two artificial lakes feeding the canal — Gatún and Alhajuela — of the water they need to operate its locks. Between May and August, precipitation in the canal's watershed came in 34% below its historical average, a shortfall that the Authority attributes to El Niño, the Pacific warming phenomenon that disrupts wind and rainfall patterns across Central America and far beyond. The stakes are considerable.

The canal carries roughly 5% of all global maritime trade and processes approximately 40% of US container traffic, serving as the principal corridor between Asian manufacturers — particularly in China — and American consumers. Its main users by volume are the United States, China, Japan, Chile, and South Korea. When the waterway slows, the cost of that slowdown travels fast: during the more severe restrictions of 2023, when daily transits were cut from 38 to just 22, auction prices for unreserved slots surged dramatically. In one recorded case this past April, a single company paid $4 million for priority passage — against a pre-crisis average winning bid of $135,000.

The Authority has already tightened draft limits for the largest vessels and warned that further reductions remain possible depending on rainfall in the coming weeks.