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A strong, long-duration M8.1 solar flare erupted from Active Region 4100 at 00:05 UTC on May 31, 2025. The flare produced a fast and significant coronal mass ejection (CME), confirmed to be Earth-directed by space weather models.<\/p>\n
Forecasts indicate the CME will reach Earth late on June 1, with initial geomagnetic storm conditions expected to reach G3 \u2013 Strong levels and a high probability of G4 \u2013 Severe storming on June 2.<\/p>\n
\u201cConfidence in an Earth-arrival component to this CME is good,\u201d SWPC forecasters said. \u201cHowever, timing and intensity are more uncertain. These watches represent potential based on our best analyses. We will not know the true nature of this CME\u2019s geomagnetic storm potential until the CME arrives at our solar wind observatories located 1 million miles from Earth.\u201d<\/p>\n
\u201cUpon arrival at those spacecraft, we will know the magnetic strength and orientation, which are very important to determine the levels and duration of geomagnetic storm conditions that are expected to occur.\u201d<\/p>\n