K-index of 4 – Geomagnetic Storm Alert issued on November 5

A K-index of 4 – Geomagnetic Storm Alert was issued by the NOAA Space Weather Prediction Center on November 5, 2025, at 01:42 UTC. The alert indicates that geomagnetic activity reached a K-index of 4 at 01:33 UTC, and the alert is active for the synoptic period from 00:00 to 03:00 UTC. This alert remains in effect, highlighting increased geomagnetic activity during this timeframe.

According to NOAA, potential impacts from this event are expected primarily poleward of 65 degrees Geomagnetic Latitude. Weak power grid fluctuations may occur in affected areas. Observers in high-latitude regions, such as Canada and Alaska, may have the opportunity to witness auroras during the period of elevated geomagnetic activity.

The alert follows a period of very high solar activity. On November 4, 2025, at 17:34 UTC, an X1.8 (R3-Strong) solar flare was observed from solar Region 4274 (N24E53). This event was associated with a partial halo coronal mass ejection (CME), although the bulk of the ejecta was anticipated to pass behind Earth. Increased geomagnetic activity can result from such solar eruptions and resulting variations in the solar wind and magnetic field near Earth.