NOAA issues a 'Severe' solar storm alert, auroras expected across most of the U.S.

At 9:46 AM Eastern Daylight Time on June 1, 2025, instruments registered a geomagnetic K-index of 8, creeping toward 9 – a level rarely reached outside the most intense solar episodes.

Such readings signal strong electric currents racing through Earth’s magnetic shield – the first sign that a severe solar storm disturbance has arrived.

Power operators, satellite controllers, and frequent flyers have good reason to pay attention. The disturbance is expected to last through at least June 3, bringing elevated radiation, intermittent radio dropouts, and a possible encore of the dazzling aurora that spilled far south earlier this spring.

Solar storms in the forecast

The National Oceanic and Atmospheric Administration’s Space Weather Prediction Center classifies the ongoing episode as G4, the second-highest rung on its five-step geomagnetic scale.

A glance at the agency’s three-day outlook shows just how busy the next 48 hours could become: the greatest expected three-hour Kp for June 1–3 averages 7.67, with individual windows pushing well into G4 territory.

Forecasters concede there is a chance – though a small one – that conditions might briefly spike to G5, the extreme category reserved for once-in-a-decade storms.

Potential impacts stretch across many modern conveniences. Power grids poleward of about 45° geomagnetic latitude may wrestle with unwanted currents that trip protective hardware. Pipelines could pick up extra voltage, accelerating corrosion.

High-frequency radio links, relied on by emergency responders and transoceanic pilots, may fade out for hours at a time.

Even the navigation apps in our pockets are not immune; satellite-based positioning can degrade or go dark until the magnetosphere settles down.

Why the sun is active

Blame an active region numbered 4100. Over the past day, it unleashed a cluster of medium-strength M-class flares, the biggest erupting at 8:05 PM EDT on May 30 with an M8.1 rating.

That flash produced a full-halo coronal mass ejection (CME) racing outward at an estimated 1,938 km/s – about 1,204 mi/s – fast enough to cross the 93 million-mile gulf between the Sun and Earth in roughly two days.

Modeling suggests the leading edge slammed into the magnetosphere around midday on June 1, aligning with the observed jump in geomagnetic indices.

Behind the main blast, solar-wind speeds had already been brisk thanks to a negative-polarity coronal-hole stream, easing from about 800 km/s on May 31 to 650 km/s just before the CME struck.

With additional flares still possible, NOAA rates the probability of minor solar-radiation storms at 75 percent each day through June 3 and pegs the odds of R1-to-R2 radio blackouts at 65 percent, with a 25 percent chance of stronger R3 events.

Ground impacts of G4 solar storms

During a severe geomagnetic storm, long transmission lines effectively turn into giant antennas. Extra current can flow through transformers, heating them and forcing operators to shed load or, in a worst-case scenario, shut down sections of the grid.

The June 1 bulletin specifically warns of “widespread voltage control problems” and the possibility that automated protection could “mistakenly trip out key assets.”

Satellite owners, meanwhile, must contend with surface charging, unexpected drag on craft in low Earth orbit, and orientation glitches that make it harder to keep antennas aimed at home.

Solar storms bring auroras

One of the perks of a strong storm is an expanded auroral oval. Forecasts hint that curtains of green and red could wander as far south as Alabama and northern California tonight and tomorrow night, weather permitting.

For many Americans, that means simply stepping outside after dark could reveal rippling colors usually reserved for Arctic latitudes.

The best views often come after local midnight, when Earth’s night side lines up with the prevailing solar-wind flow.

What happens next?

NOAA’s hour-by-hour breakdown shows Kp values flirting with 8 or higher through the late afternoon of June 1, settling toward G2 conditions by midday June 3. Even after the peak passes, residual turbulence in the solar wind can keep magnetometers lively.

Because the timing and strength of CME impacts hinge on the magnetic orientation of the cloud, forecasters caution that confidence in exact numbers is lower than usual.

The present solar cycle is only midway to its expected summit, and activity has already outpaced early predictions.

As the Sun moves toward maximum, bursts like this one will become more common, offering both scientific bonanzas and practical headaches.

Utilities have hardened equipment since the famous March 1989 blackout in Québec, yet the number of satellites, drones, and cable-linked infrastructure has soared. Every severe storm serves as a stress test – and a reminder – to keep contingency plans up to date.

Protecting technology during the storm

Individuals can take simple steps while the geomagnetic field roils. Unplugging non-essential electronics during the most intense intervals reduces the chance of burnout from voltage spikes.

Amateur radio operators should expect HF quiet zones and can switch to lower-frequency or digital modes until propagation rebounds.

Farmers and surveyors who depend on high-precision GPS may want to delay fieldwork, as centimeter-level fixes can wobble by several yards when space weather flares.

Professional networks rely on well-timed data to synchronize transactions, steer trains, and balance grids. When navigation satellites falter, those systems fall back on atomic clocks and fiber connections.

Engineers run drills for exactly this scenario, but the real-world rehearsal now unfolding will reveal whether procedures hold up under G4 stress.

Stay alert and watch the night skies

A single full-halo CME has turned an otherwise quiet Sunday into a laboratory for space-weather science and risk management.

With K-index readings near 8, solar-radiation storm chances at 75 percent, and radio-blackout odds topping 65 percent, the next two days demand attention from anyone who depends on reliable power, navigation, or radio links – which is to say, almost everyone.

Once the magnetosphere calms, researchers will sift through data to refine models, but for now the message is simple: stay informed, stay prepared, and, if clouds cooperate, enjoy the show lighting up the night.

Check in with the Space Weather Prediction Center for updates and more information.

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