G1 – Minor Geomagnetic Storm Watch issued for September 16–17, 2026

A G1 – Minor Geomagnetic Storm Watch was issued for September 16–17, 2026. The highest predicted geomagnetic storm level is G1 – Minor on both September 16 and 17. This Watch supersedes all prior watches in effect.

Potential impacts are most likely in regions poleward of 60 degrees geomagnetic latitude. Weak power grid fluctuations may occur as a result of induced currents. There is a possibility of minor impacts to satellite operations. Auroras may become visible at high latitudes, including the northern tier of the United States, such as northern Michigan and Maine.

The forecast discussion attributes this event to effects from a negative polarity coronal hole high-speed stream (CH HSS), which are expected to persist through September 17. Additional geomagnetic enhancements are possible on September 16 and 17 due to the influence of coronal mass ejections (CMEs) that departed the Sun on September 13 and 14, 2026.