ALERT: Geomagnetic K-index of 4 Alert issued on May 4

A Geomagnetic K-index of 4 Alert was issued by NOAA SWPC on May 4, 2026, at 16:49 UTC. The alert indicates that the geomagnetic K-index reached a value of 4 during the synoptic period from 15:00 to 18:00 UTC on May 4, 2026. This alert signifies minor geomagnetic activity primarily affecting regions poleward of 65 degrees Geomagnetic Latitude.

Potential impacts from this alert include weak power grid fluctuations in the affected areas. Additionally, auroral displays may be visible at high latitudes such as Canada and Alaska. These impacts are typical for this alert level and do not generally pose a risk to infrastructure outside the high-latitude regions.

The alert was triggered during a period when solar wind parameters were under the influence of a weak negative polarity coronal hole high-speed stream. Solar wind speeds declined and no significant sustained deflections in the interplanetary magnetic field were observed. No Earth-directed coronal mass ejections were detected in available imagery, and the overall geomagnetic field activity was reported as quiet to unsettled. The environment is expected to return to quieter conditions as these coronal hole influences wane.