Alert – Geomagnetic K-index of 4 issued on June 11, 2026

A Geomagnetic K-index of 4 Alert was issued by the NOAA Space Weather Prediction Center at 18:57 UTC on June 11, 2026. The K-index threshold of 4 was reached at 18:55 UTC, and the alert is valid for the synoptic period 18:00 to 21:00 UTC. This indicates that geomagnetic conditions have increased to active levels.

Impacts are expected primarily poleward of 65 degrees geomagnetic latitude. According to the alert, weak power grid fluctuations may occur due to induced currents. In addition, auroras may be visible at high latitudes, such as in Canada and Alaska.

The space weather forecast discussion attributes these unsettled geomagnetic conditions to the arrival of a corotating interaction region (CIR) preceding the onset of a negative polarity coronal hole high speed stream (-CH HSS). Elevated solar wind conditions are expected to continue through June 13, 2026, with a chance for further enhancements from combined influences of coronal mass ejections (CMEs) that departed the Sun on June 9 and June 11, 2026.