ALERT: Geomagnetic K-index of 4 – Geomagnetic Storm Alert issued on October 31

A Geomagnetic K-index of 4 ALERT was issued by the NOAA Space Weather Prediction Center on October 31, 2026. The threshold was reached at 18:45 UTC, and the alert covers the synoptic period from 18:00 to 21:00 UTC. An active warning is in effect, indicating geomagnetic disturbances at levels that may affect specific regions.

Potential impacts are primarily expected poleward of 65 degrees geomagnetic latitude. The alert notes that weak power grid fluctuations can occur due to induced currents. Additionally, auroras may be visible at high latitudes, such as across parts of Canada and Alaska, during this period.

According to the official forecast discussion issued on October 31, 2026, at 12:30 UTC, the current geomagnetic activity is linked to enhanced solar wind parameters resulting from a positive polarity coronal hole high-speed stream (CH HSS). No Earth-directed coronal mass ejections were detected. Geomagnetic conditions are likely to remain elevated through November 2 as CH HSS influence continues, with the geomagnetic field expected to reach G1 (Minor) geomagnetic storm levels on October 31 and November 1.