ALERT – Geomagnetic K-index of 4 Alert issued on September 24

A Geomagnetic K-index of 4 Alert was issued on September 24, 2026, by the NOAA Space Weather Prediction Center. The alert was triggered at 09:45 UTC and is valid for the synoptic period from 09:00 UTC to 12:00 UTC. The alert remains active with a warning in effect.

Potential impacts are primarily expected poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations can occur due to induced currents. There is also a chance for aurora to be visible at high latitudes, such as Canada and Alaska. These impacts reflect typical activity at this K-index level.

According to the latest forecast discussion, the alert was triggered by enhanced solar wind conditions due to the arrival of a positive polarity coronal hole high speed stream (CH HSS) during the first half of September 24. Enhanced geomagnetic conditions are expected to persist through September 25 before gradually subsiding toward September 26.