G3 – Strong Geomagnetic Storm Watch issued for June 4 and 5, 2026

A G3 – Strong Geomagnetic Storm Watch was issued for June 4 and June 5, 2026. The watch, released by NOAA SWPC on June 3, 2026 at 14:52 UTC, indicates that strong geomagnetic storm conditions are expected on these days. No geomagnetic storming above G1 is forecast for June 6. This watch supersedes all previous watches in effect.

A G3 – Strong Geomagnetic Storm means that significant geomagnetic disturbances are anticipated. During these conditions, power systems, spacecraft operations, and radio communications may experience potential impacts. The highest storm level predicted by day is G3 (Strong) for both June 4 and June 5, after which conditions are expected to subside to below G1 levels. Operators of affected systems should remain attentive to updated forecasts and official SWPC guidance during this interval.

The elevated geomagnetic storm risk is linked to recent high solar activity from Active Region 4455, which produced two moderate (R2) solar flares (M9.3 at 03/0136 UTC and M7.7 at 03/0700 UTC) and one strong (R3) X1.0 flare at 03/1128 UTC. Each of the two M-class flares was associated with a coronal mass ejection (CME), with both showing evidence of Earth-directed components, as indicated by LASCO, GOES/SUVI, and STEREO coronagraph imagery. Modeling continues to further detail the CME impacts, but NOAA SWPC forecasts elevated solar wind conditions associated with these events, leading to a strong geomagnetic response in the near-Earth environment on June 4–5, 2026.