Minor Geomagnetic Storm Forecast for October 2, 2026

A minor geomagnetic storm is forecast for October 2, 2026, following a glancing blow from a coronal mass ejection. NOAA’s Space Weather Prediction Center issued a G1, Minor geomagnetic storm watch at 13:01 UTC on September 29. The event stems from a large solar filament eruption observed lifting off at about 13:51 UTC on September 28. A partial-halo coronal mass ejection associated with the eruption was first seen at 14:36 UTC that same day. The Solar Influences Data Analysis Center at the Royal Observatory of Belgium estimated the ejection's speed near 500 kilometers per second. Most of the material was directed westward, setting up a glancing encounter with Earth.

Forecast models indicate minor storm arrival

Multiple forecast models predict the coronal mass ejection's arrival on October 2. The SWPC forecast shows no storm-level activity for September 30 or October 1. G1 conditions are likely on October 2. In its three-day forecast, the center placed the highest forecast three-hour planetary K-index at 4.67. This is equivalent to Kp 5-, the threshold for a G1 minor storm, during the period of 15:00 to 18:00 UTC on October 2.

A deterministic model from NASA's Community Coordinated Modeling Center predicted shock arrival near Earth at approximately 03:15 UTC on October 2, with an uncertainty of plus or minus seven hours. That model run placed the possible maximum geomagnetic response between Kp 3 and Kp 5. A separate 27-member ensemble model produced an average arrival time of 00:05 UTC on October 2. The coronal mass ejection's leading edge reached missions near Earth between 16:25 UTC on October 1 and 06:42 UTC on October 2 in ninety-six percent of the simulations. The ensemble assigned a ninety-five percent chance that the maximum Kp would remain between 2 and 4, which is below the G1 threshold.

Expected effects and aurora visibility

The impending G1 storm is the lowest category on NOAA's five-level geomagnetic storm scale. It may cause weak power grid fluctuations. Minor effects on satellite operations are also possible. The primary visible effect for the public will be auroras. They may become visible at high latitudes, including parts of the northern U.S. Tier such as northern Michigan and Maine. The SWPC alert specifically names those two states as places where auroras are likely to be seen. Auroras may extend further south than usual due to the geomagnetic storming and increased planetary K-index. Residents of many more northern U.S. States could view them if conditions extend.

Viewing conditions and timing

Best aurora viewing is expected at night around midnight. Peak geomagnetic activity based on the planetary K-index, however, is expected between 10 am and 1 pm Central Daylight Time on October 2. The mainland U.S. will be in daylight during that peak. Increased levels of incoming solar plasma are expected throughout the day. High vantage points around dark sky sites with low light pollution offer the best viewing experience. With an unobstructed view of the northern horizon, auroras up to six hundred miles further north may be visible. Auroras can be visible even when space weather conditions do not reach storm levels. The September equinox occurred on September 22. The Russell-McPherron effect causes auroras to be more pronounced around equinoxes. Independent March and October have the highest number of days with visible auroras.

During the twenty-four hours preceding the forecast, the greatest observed three-hour planetary K-index was 2. That is below NOAA's Space Weather Scale levels. Peak geomagnetic activity based on the planetary K-index is expected between 10 am CDT and 1 pm CDT on October 2.