Alert – Geomagnetic K-index of 4 Alert issued on June 19

A Geomagnetic K-index of 4 Alert was issued by NOAA’s Space Weather Prediction Center on June 19, 2025. The alert indicates that the threshold was reached at 20:38 UTC during the synoptic period from 18:00 to 21:00 UTC, and an active warning is currently in effect.

The alert specifies that the area of impact will primarily be poleward of 65 degrees Geomagnetic Latitude. Potential effects include weak power grid fluctuations due to induced currents. Additionally, aurora may be visible at high latitudes, such as Canada and Alaska.

This alert was triggered during a period of quiet to unsettled geomagnetic field activity, driven by continued effects from a coronal hole high speed solar wind stream. No Earth-directed coronal mass ejections (CMEs) were observed in available solar imagery during this period.