ALERT: Geomagnetic K-index of 4 – Geomagnetic Storm Alert issued on October 16

A Geomagnetic K-index of 4 Alert was issued by NOAA SWPC on October 16, 2026. The alert became effective when the K-index reached 4 at 19:40 UTC, covering the period between 18:00 and 21:00 UTC. The alert remains active as of the time of issue.

Potential impacts include effects primarily poleward of 65 degrees geomagnetic latitude. Weak power grid fluctuations may occur due to induced currents, and aurora may be visible at high latitudes such as Canada and Alaska. These impacts are consistent with typical space weather conditions described for this alert level by the NOAA Space Weather Scale.

According to the latest forecast discussion, geomagnetic field activity was triggered by slightly elevated solar wind conditions associated with diminishing high-speed stream activity from a negative polarity coronal hole. No Earth-directed coronal mass ejections were observed. Unsettled geomagnetic conditions are anticipated to persist through October 16 as influences from the coronal hole high-speed stream wane, with quieter conditions expected to return on October 17 and persist through October 18.