G1 – Minor Geomagnetic Storm Alert issued on October 18, 2025

A G1 – Minor Geomagnetic Storm Alert was issued on October 18, 2025. The geomagnetic K-index reached 5 at 19:47 UTC during the synoptic period of 18:00 to 21:00 UTC. The alert indicates that active warning conditions are present according to NOAA SWPC.

Potential impacts from this G1 – Minor Geomagnetic Storm are expected primarily poleward of 60 degrees geomagnetic latitude. Weak power grid fluctuations can occur, and minor impact on satellite operations is possible. In addition, aurora may become visible at high latitudes, including the northern tier of the United States such as northern Michigan and Maine.

According to NOAA SWPC discussion, the geomagnetic disturbance is likely related to glancing influences from coronal mass ejections (CMEs) that left the Sun between October 13 and 15. Forecast models suggest any such effects could elevate geomagnetic activity to G1 – Minor levels by late on October 18, 2025.