Solar Storm
A strong geomagnetic storm can disrupt the power grid, GPS, and radio communications, and in the extreme case (NOAA scale level G5), can trigger a widespread blackout. The most effective preparation is the same as for a power outage: have light, water, cash, and a battery-powered radio on hand. Follow official information via radio and Alertswiss, and expect GPS and radio communication inaccuracies.
A solar storm begins with a solar flare and often with a coronal mass ejection (CME) – a massive cloud of plasma hurled into space. When it reaches Earth, a geomagnetic storm forms. The radiation from the flare reaches Earth in roughly 8 minutes (speed of light), the slower plasma cloud typically in 1 to 3 days. This time window is also the advance warning period, during which grid operators monitor space weather via the NOAA Space Weather Prediction Center (SWPC).
The primary danger to Switzerland is geomagnetically induced currents (GICs) in long high-voltage transmission lines: they can saturate and overheat transformers and, in the extreme case, trigger a widespread power outage. Additionally, strong storms disrupt GPS/GNSS, shortwave radio communications on the day side, and can damage satellites. The NOAA measures geomagnetic storms on a scale from G1 (minor) to G5 (extreme).
Extreme storms are rare, but real: in May 2024, a G5 storm occurred for the first time since 2003. The most effective private preparation is the same as for a power outage – light, water, cash, and a battery-powered radio. Regarding the exact probability of recurrence of a Carrington-type century event, scientific estimates vary; it is therefore given only as a range.
Solar Cycle – Where We Stand
Solar Cycle 25: Descending Phase – peak reached in October 2024 (NASA/NOAA)
Why it matters: Around solar maximum, sunspots are most numerous – and therefore solar flares, coronal mass ejections, and powerful geomagnetic storms occur much more frequently than at solar minimum. The peak of Cycle 25 was reached in October 2024; since then we are in the descending phase, which experience shows continues to bring severe storms — the strongest storm in roughly 20 years (the G5 "Gannon" storm) occurred in May 2024. For Switzerland, the main risk is that of geomagnetically induced currents in the power grid: in 1989, such a storm paralyzed the grid of the Canadian province of Quebec in about 90 seconds and left about 6 million people without electricity.
Risk rating
Likelihood: Low · Impact: High → Overall risk: Medium.
| Impact | |||
|---|---|---|---|
| Low | Medium | High | |
| High | |||
| Medium | |||
| Low | This hazard's rating | ||
Legend: Low (green) · Medium (yellow) · High (red). Overall risk is likelihood multiplied by impact.
A powerful geomagnetic storm can disrupt power grids, GPS, and radio communications. In extreme cases, a widespread blackout threatens — preparations similar to those for a power outage help.
Immediate measures
- If blackout risk: activate the same preparations as for a power outage
- Have a battery-powered/hand-crank radio ready for information
- Expect inaccuracies in GPS/radio communications
Warning signs
- Storm warning from NOAA SWPC (geomagnetic scale G1 to G5)
- Aurora visible unusually far south (into Central Europe) – sign of a strong storm
- Notable GPS/GNSS inaccuracies and shortwave radio interference
- Reports from power grid operators of increased load
- Official warnings via radio and Alertswiss
Before · During · After
Before
- Keep basic blackout supplies on hand: light, water, cash, power bank
- Hand-crank/battery-powered radio (FM/DAB+) for receiving information
- Understand that grid operators take countermeasures when warned in advance
During
- Follow official information via radio and Alertswiss
- If a power outage occurs, apply the measures outlined in the power outage scenario
- Critically verify GPS/navigation data, use alternatives
- Disconnect sensitive equipment from the grid if necessary
After
- Check equipment and connections after the disturbance
- Replenish supplies and cash reserves
- Await official all-clear and situation reports
This really happened
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2024 Gannon Storm
In May 2024, the strongest geomagnetic storm since 2003 (G5) occurred; GPS and radio disturbances happened worldwide, and power suppliers had to actively stabilize their grids. Aurora was visible as far south as Switzerland.
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2022 Starlink Satellite Loss
A geomagnetic storm greatly increased atmospheric drag in low Earth orbit on February 3, 2022; about 40 of 49 newly launched Starlink satellites could not maintain their orbits and burned up — an example of the direct technical consequences of space weather.
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2017 Strongest Solar Flare Since 2005
On September 6, 2017, the Sun emitted a flare of the highest class (X9.3) — the strongest since 2005. The resulting radiation disrupted shortwave radio traffic, which is used for ships, aircraft, and emergency radio communications.
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1989 Quebec Blackout
On March 13, 1989, a geomagnetic storm caused a grid collapse in the Canadian province of Quebec in minutes; about six million people lost electricity for about nine hours.
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1859 Carrington Event
The strongest geomagnetic storm ever recorded (September 1-2, 1859) caused arcing in telegraph lines worldwide and sometimes set them on fire – a comparable event today would affect a much more tightly interconnected infrastructure.
Source
Frequently asked questions
How much advance warning is there before a solar storm?
A solar storm begins with a solar flare and often a coronal mass ejection (CME). The radiation from the flare reaches Earth at the speed of light in roughly 8 minutes, while the slower plasma cloud typically arrives in 1 to 3 days. This time window is also the advance warning period, during which grid operators monitor space weather via the NOAA Space Weather Prediction Center and take countermeasures.
Why is a solar storm dangerous for Switzerland?
The primary danger is geomagnetically induced currents (GICs) in long high-voltage transmission lines: they can saturate and overheat transformers and, in the extreme case, trigger a widespread power outage. Additionally, strong storms disrupt GPS/GNSS, shortwave radio communications on the day side, and can damage satellites. The NOAA measures geomagnetic storms on a scale from G1 (minor) to G5 (extreme).
When was the last major solar storm?
In May 2024, a G5 storm occurred for the first time since 2003 with the Gannon storm; GPS and radio disturbances occurred worldwide, and aurora was visible as far south as Switzerland. Historically, the Carrington Event of 1859 is considered the strongest storm ever recorded. How often such a century-scale event recurs is estimated by science only as a range — a fixed value would be unreliable.
What phase of the solar cycle are we in, and why does that increase storm risk?
We are in Solar Cycle 25, whose peak phase was announced as reached by NASA and NOAA on October 15, 2024. Since then, sunspot numbers have been declining slowly – as of early 2026, we are in the declining phase. This is not an all-clear: around the peak and in the years that follow, solar flares, coronal mass ejections, and geomagnetic storms occur much more frequently and with greater intensity than during solar minimum, and some of the strongest storms occurred only after the actual peak. Moreover, the exact timing of the peak can only be reliably determined in hindsight. Preparedness therefore remains relevant.
Official sources
- NOAA SWPC Space weather and storm alerts (G scale)
- Alertswiss Current notifications
- OSTRAL Electricity shortage