The updated month 1-4 climate outlook for the U.S. features increasing forecast confidence based on the influence on North America climate by dramatic cool phase of the Pacific decadal oscillation and warm phase of the Atlantic multi-decadal oscillation. A weak ENSO regime has limited influence.

During September 2024 the sea and ice concentration within the polar ice cap is 4th lowest in the 1978-2024 climatology. By comparison, the polar ice cap is considerably smaller than typical of 40+ years ago. The modern-day constricted polar ice cap has contributed to a recent trend of above normal snow cover developing early in the northern hemisphere cold season.

The below normal activity in each basin is unusual. The reasons for the below normal activity are under review. In the Northwest Pacific, high-level above normal westerly wind shear across the tropics has limited hurricane development while stronger than normal low-level trade winds have suppressed activity in the deep tropics of the Northeast Pacific and North Atlantic.