The Northwest Seaport Alliance (NWSA), encompassing the ports of Seattle and Tacoma, reported a significant year-over-year (YoY) decline in cargo volumes, with August 2025 numbers dropping 18.7% compared to August 2024. The trend continued into early September, with key metrics for the week ending September 12 showing steep declines compared to the same period last year.

For the week ending September 12, international imports, truck transactions, and vessel lifts were all down compared to the September 2024 weekly average.

• International import containers were down 23.0%.

• Truck transactions saw a 23.6% decrease.

• Vessel lifts (containers moved on or off a ship) fell by 16.6%.

The decline is especially noteworthy as it occurs during what is typically the supply chain's peak season. September is traditionally one of the NWSA's busiest months, as retailers and beneficial cargo owners (BCOs) stock up on holiday merchandise. However, port officials do not expect a typical peak season this year, which usually extends into October.

According to market intelligence from the NWSA, this year's peak season largely occurred earlier than usual, with shippers advancing cargo into July and other earlier months to get ahead of tariffs. This deviation from standard shipping patterns has made it difficult to track overall volumes.

The report suggests the drop is partly attributable to tariff impacts. Another factor inflating last year's metrics was a disruption at Canadian ports, which diverted additional cargo to the NWSA. Exports have also been affected, falling 18.1% in August, as they depend on the vessel and rail availability driven by import volumes.

While weekly numbers for September 12 showed a decrease from the prior year, there was a week-over-week increase in activity compared to the first week of September. International imports rose 27.2%, truck transactions were up 22.2%, and vessel lifts increased by 11.4% from the week ending September 5.

Even so, the overarching trend points to a significant year-over-year slowdown for the major Pacific Northwest gateway.