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

A Geomagnetic K-index of 4 Alert was issued on October 4, 2026, by the NOAA Space Weather Prediction Center. The alert was triggered at 07:57 UTC and is valid for the synoptic period from 06:00 to 09:00 UTC. The alert remains active.

According to the official alert, potential impacts are expected primarily poleward of 65 degrees geomagnetic latitude. Weak fluctuations in power grids may be observed due to induced currents. Auroras may be visible at high latitudes, such as in Canada and Alaska.

The latest forecast discussion attributes this geomagnetic activity to enhanced solar wind conditions resulting from the influence of a coronal hole high-speed stream (CH HSS). Elevated geomagnetic activity is anticipated to persist through October 5, with conditions expected to decline by October 6, 2026.