G1 – Minor Geomagnetic Storm Alert issued on October 18

A G1 – Minor Geomagnetic Storm Alert was issued for October 18, 2025. The alert, marked by a geomagnetic K-index of 5, was triggered at 17:46 UTC and covers the synoptic period from 15:00 to 18:00 UTC. This alert represents a minor level of geomagnetic storming based on NOAA’s official classification and indicates that an Active Warning is currently in effect.

Potential impacts are expected primarily poleward of 60 degrees geomagnetic latitude. Minor impacts may include weak fluctuations in power grids and minor issues for satellite operations. There is also a possibility of auroras being visible at high latitudes, such as in the northern tier of the U.S., including states like northern Michigan and Maine.

According to the latest forecast discussion from NOAA SWPC, this geomagnetic storm activity is likely related to glancing influences from Coronal Mass Ejections (CMEs) that departed the Sun between October 13 and 15, 2025. Model results suggest a minor impact at Earth late on October 18 as the bulk of the CME material moves ahead of Earth’s orbit. Additional unsettled to active conditions are anticipated to continue into early October 19, followed by further effects from a negative polarity Coronal Hole High-Speed Stream.