ALERT: Geomagnetic K-index of 4 Alert issued on June 25, 2026

A Geomagnetic K-index of 4 Alert was issued by NOAA SWPC on June 25, 2026, at 19:41 UTC. The alert indicates elevated geomagnetic activity, with the K-index reaching 4 during the synoptic period from 18:00 to 21:00 UTC. The alert remains active and advises that high-latitude regions may be affected during this period.

Potential impacts from this event are expected primarily poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations can occur due to induced currents, and auroras may be visible at high latitudes, including areas such as Canada and Alaska. These impacts are in line with NOAA’s scale for geomagnetic disturbances at this level.

The alert was triggered by elevated solar wind conditions associated with the onset of a negative polarity coronal hole high speed stream (CH HSS) and possible minor magnetic transient influences. Solar wind speeds increased significantly, with accompanying variations in the magnetic field and geomagnetic conditions rising to active levels as a result. These disturbed solar wind parameters are expected to persist through at least June 27, 2026.