September: A critical month for global sea ice

Arctic and Antarctic sea ice wax and wane in opposite seasonal patterns, as befits their respective hemispheres. That makes September a key month, in which the ice reaches a low at one pole and a high at the other. Here's how 2025 looks in a dataset going back to late 1978: No new records, but relatively low ice levels at both poles for this time of the year.

The data show the 5 day trailing mean value for ice extent in million square kilometers, from late 1978 through the present. The gap seen near the beginning of March is because only one in four years (leap years) have a value for February 29. The data are currently updated through October 20, 2025.
Chart: Chris MooneySource: National Snow and Ice Data CenterCreated with Datawrapper