Tropical storms and Hurricane Hermine combined to slow the movement of oil tankers and shut in offshore drilling, forcing the U.S. oil industry to dip into its massive oversupply at the highest rate for this time of year.

In the past week, the industry used 14.5 million barrels in storage, largely from the East Coast and Gulf Coast, according to government data. Analysts blamed wind and rough seas resulting from Gaston, Hermine and other storms that have impeded ships with cargoes headed for U.S. refineries.