There were 40 container vessels waiting to offload at the adjacent ports of Los Angeles and Long Beach in Southern California as of Wednesday, the most since Bloomberg developed an index tracking port congestion globally.

On the East Coast, Georgia’s Port of Savannah had 20 cargo carriers idling in queue, compared with just eight in port -- the highest congestion rate of all major ports in the world. At the Port of New York and New Jersey, the queue swelled to its highest since April as well.

Port congestion is worsening during one of the calendar year’s two peak seasons for global shipping demand. In the U.S. and elsewhere, bottlenecks along all modes of freight transportation are delaying deliveries for retailers and manufacturers, sapping capacity and driving cargo costs to record highs.

In China, congestion off the docks at Ningbo has eased considerably since numbers soared at the end of August, but some of that traffic was dispersed and led to higher counts off regional gateways like Qingdao, which also recorded its highest waiting ship tally since August.

Bloomberg’s container ship index counts container activity in three ways: the number of overall vessels in a port’s anchorage area, the number of anchored or waiting ships, and the congestion rate of anchored ships waiting as a share of those in port.