The Northwest Seaport Alliance (NWSA), encompassing the ports of Seattle and Tacoma, reported a general downturn in its weekly volumes and metrics for the final full week of August, with most key indicators showing declines. The data, released in its September 10, 2025, Weekly Volumes & Metrics Report, indicated a continuation of week-over-week fluctuations, though truck transactions provided a solitary bright spot.

International imports for the week ending August 29 were down 26% from the prior week and 18.6% compared to the August 2024 weekly average. A total of 12,688 containers were imported during this period, which is 1.3% less than the 2025 year-to-date average and 6.7% below the 2024 weekly average.

Vessel lifts, which include the movement of containers on and off ships, also saw a significant decrease, falling 20.6% week-over-week and 19.2% when compared to the August 2024 weekly average. The NWSA recorded 25,034 vessel lifts for the week ending August 29, reflecting a 7.6% decline from the 2025 year-to-date average.

In contrast to the overall decline, truck transactions showed an increase, up 14.4% compared to the week prior. This surge in activity, totaling 24,559 truck transactions for the week ending August 29, is "likely moving cargo from the busy week prior". Despite this week-over-week increase, truck transactions were still 13.8% lower than the August 2024 weekly average, although 2.0% above the 2025 year-to-date average.

Vessel calls to the NWSA facilities also experienced variations in late August and early September. After seeing 14 voyages (with 1 void) for the week ending August 22, the number dropped to 12 voyages (with 1 void and 1 delayed arrival) for the week ending August 29, and further to 10 voyages (with 2 voids and 1 delayed arrival) for the week ending September 5. The forecast for the week ending September 12 anticipates 13 voyages with 2 voids.

In addition to operational metrics, the NWSA is closely monitoring external factors that could impact trade. The alliance is tracking a recent U.S. court of appeals decision on tariffs, a case that has since been elevated to and accepted by the Supreme Court. The outcome of this case could have significant implications for international trade volumes moving through the gateway.