NOAA warns G2 geomagnetic storm

NOAA’s Space Weather Prediction Center said on Saturday, May 16, that Earth had seen G2, or moderate, geomagnetic storm conditions within the previous 24 hours, while forecasters expected weaker G1 conditions for the rest of Saturday and into Sunday. The agency’s public dashboard showed the “24-Hour Observed Maximums” at G2 and listed a G1 forecast for May 16 and May 17. NOAA’s aurora dashboard said the strongest expected three-hour planetary Kp reading for May 16 through May 18 was 5.67, which corresponds to G2 conditions. ### What did NOAA actually forecast for Saturday, May 16? NOAA’s latest public forecast, issued at 0030 UTC on May 16, said the greatest expected three-hour Kp level for May 16-May 18 was 5.67, or G2 on NOAA’s scale. The same forecast broke that down into a G2 reading for the 00-03 UTC period on May 16, followed by G1 or lower levels in later periods. (swpc.noaa.gov) The Space Weather Prediction Center homepage on Saturday showed “Predicted 2026-05-16 UTC … G1 minor” and “Predicted 2026-05-17 UTC … G1 minor,” indicating that by the time of the latest dashboard update, forecasters were no longer showing a full-day G2 outlook. NOAA’s site also listed the latest observed geomagnetic storm level as “G none,” even as the 24-hour maximum remained G2, showing that storm intensity had eased after the earlier peak. (swpc.noaa.gov) ### Why are reports talking about both G2 and G1? NOAA uses separate measures for observed conditions and forecast conditions, and the agency’s pages showed both on Saturday. The “24-Hour Observed Maximums” field recorded a G2 event, while the forecast fields for May 16 and May 17 showed G1. Forbes reported on May 13 that a G2 storm could expand aurora visibility beyond the usual northern tier, while a May 15 Forbes report said Friday night’s setup had narrowed to a 10-state viewing zone under G1 conditions. (swpc.noaa.gov) Those reports matched the shift visible in NOAA’s public products from a stronger short-window forecast to weaker conditions later in the weekend. ### What causes a geomagnetic storm like this? NOAA said its alerts, watches and warnings describe the severity of solar activity expected to affect Earth’s environment. Independent reports citing NOAA said this episode was tied to a high-speed solar wind stream from a coronal hole, a darker region in the sun’s upper atmosphere where solar wind can escape more easily. (forbes.com) The aurora dashboard said geomagnetic storm levels are tied to the planetary Kp index, with Kp 5 equal to G1 and Kp 6 equal to G2. Saturday’s forecast table showed how those values can rise and fall over three-hour blocks rather than hold steady all night. ### Does the new moon help people see the aurora? (swpc.noaa.gov) The U.S. Naval Observatory said May 16, 2026, is a new moon, with 0% of the moon’s visible disk illuminated. Darker skies do not create auroras, but they make faint displays easier to see, especially away from city lights. (swpc.noaa.gov) Timeanddate’s 2026 moon-phase calendar also lists a new moon on May 16. That means skywatchers looking north on Saturday night face less interference from moonlight than they would during a brighter lunar phase. ### Where should people look for the latest view? NOAA’s aurora dashboard says it provides a forecast for “tonight and tomorrow night” and includes near-real-time estimates for the next 30 minutes. (aa.usno.navy.mil) The agency’s homepage and alerts page also show current conditions, forecast storm levels and any navigation or radio impacts tied to space weather. (timeanddate.com) Saturday’s NOAA pages showed solar wind speed at 694 km per second and listed G1 minor conditions as the forecast for May 17, with no geomagnetic storm forecast for May 18. The next public updates are on NOAA’s Space Weather Prediction Center dashboards and forecast products as conditions change through the weekend. (swpc.noaa.gov 1) (swpc.noaa.gov 2)