Case Study · Solar Flare · 2024
May 10–13, 2024. The strongest geomagnetic storm in 21 years struck Earth — a G5, the most severe category. NOAA warned of possible widespread voltage control problems, complete grid collapses, and transformer damage. Northern Lights appeared in Texas, Florida, and Southern California. And the power grid held. The 35 years of investment in grid hardening and space weather forecasting made after 1989's Quebec blackout worked exactly as intended.
Earth · May 10–13, 2024
In early May 2024, sunspot region AR3664 — a large, complex active region on the sun's surface — began producing a series of increasingly powerful solar flares. The Wikipedia account of the May 2024 solar storms documents the sequence: X1.0 and multiple M-class flares on May 8; X2.25 and X1.12 flares on May 9; X3.98 on May 10; X5.4-5.7 on May 11. Multiple coronal mass ejections were launched toward Earth in quick succession. Some were "catching up with other ones," as NOAA Space Weather Prediction Center service coordinator Shawn Dahl told reporters on May 10 — merging into a compound event. When they arrived on May 10–11, the geomagnetic disturbance reached the G5 (Extreme) level — the highest on the NOAA scale. The Kp-index peaked at 9, the Dst index reached −412 nT, and the Ap-index reached 271. These numbers place the May 2024 storm as the most intense since the 2003 Halloween storms and definitively the first G5 event since October 2003.
NOAA's formal warning for a G5 storm is explicit about the possible consequences: "Widespread voltage control problems and protective system problems can occur. Some grid systems may experience complete collapse or blackouts. Transformers may experience damage." CBS News repeated this warning verbatim. NOAA issued its first watch for a potential G4-level storm in almost 20 years. Meteorologists and emergency managers prepared. Utility operators activated their space weather protocols. And across the Northern and Southern hemispheres, people who had never seen the Northern Lights stepped outside and watched them flicker green, red, and purple in skies far south of their normal range — from Texas, Alabama, and Southern California to New Zealand and Australia. The storm was real, large, and visible. And the major power outages that NOAA had warned might occur did not materialize in North America or Europe.
May 10–13, 2024
Date
G5
Storm Level
First since 2003
G5 in 21 years
Texas, Florida
Aurora Visible
Grid Held
No Major Outages
The absence of major outages during the May 2024 G5 storm is the most important data point in the modern solar weather preparedness record. The 1989 Quebec blackout was caused by a storm that Dr. David Boteler described as "the biggest geomagnetic storm of the Space Age." The 2024 storm, while not quite as intense as 1989 at peak disturbance (Dst −412 nT vs. approximately −600 nT in 1989), was comparable in G-scale classification and clearly capable of producing grid damage under 1989-era grid conditions. That it did not produce major grid failures in North America or Europe in 2024 reflects the 35 years of improvements driven by 1989's lesson: adjusted relay sensitivity, NERC GIC reliability standards, transformer neutral blocking devices, real-time GIC monitoring systems, and the advance warning from NOAA's Space Weather Prediction Center that allowed grid operators to take protective actions before the CMEs arrived.
The Science
Think of the 1989 Quebec failure as a cascade that began with protective relays incorrectly tripping under GIC-induced harmonic conditions. Hydro-Québec's fix — reducing relay sensitivity thresholds — was the core technical intervention. In the 35 years after 1989, this fix was applied progressively across North American utilities, alongside additional measures: transformer neutral blocking devices (which interrupt the path through which GICs flow into transformer cores), real-time GIC monitoring systems that let operators see induced currents before they cause problems, and revised operational procedures that allow grid operators to manually shed load or adjust reactive power during geomagnetic storms to maintain voltage stability. NERC's TPL-007 standard codified many of these requirements. The combination of technical protection and operational procedures is what allowed grid operators to manage through a G5 event in 2024 without the 1989-style cascade.
The space weather forecasting infrastructure — the DSCOVR satellite at L1, the GOES solar instruments, and NOAA's Space Weather Prediction Center — provided 1–3 days of advance warning between the detection of the CMEs from AR3664 and their arrival at Earth. This warning window allowed utility operators to review their GIC monitoring systems, alert relevant personnel, and prepare to execute protective procedures. The NPR/NOAA account documents that NOAA had "notified airlines, NASA, the Federal Aviation Administration, the Federal Emergency Management Agency, the North American Electric Reliability Corporation and other operators to prepare for the storm." This coordination — possible only because of the monitoring infrastructure — is what enabled a managed rather than surprised response. The 1989 Quebec blackout struck at 2:44 AM with essentially no notice. The 2024 G5 storm was forecast days in advance.
The 2024 G5 storm, while the largest in 21 years, was not at Carrington-level magnitude. The 1859 Carrington Event is estimated to have been 2–3 times more intense than the 1989 Quebec storm. The July 2012 solar storm that missed Earth by 9 days was estimated by NASA scientists to be of Carrington-class magnitude. A Carrington-class event direct hit would test the current grid protections far beyond what 2024 tested. The protections that worked in 2024 are genuine progress from 1989. They are not a guarantee against a 1859-scale event. The correct reading of the 2024 result is: the investments after 1989 worked for a G5 storm of this magnitude. The question of whether they are sufficient for a larger event remains open — and the answer depends on continued investment in grid hardening beyond what the current NERC standards require.
Timeline
01
Early May 2024: Sunspot region AR3664 develops — large, complex, highly active during Solar Cycle 25's approach to maximum. May 8–9: X1, M-class, X2.25, X1.12 flares; multiple halo CMEs launched toward Earth. May 9: NOAA issues first G4 storm watch in nearly 20 years. May 10: NOAA confirms some CMEs "catching up with other ones" — compound event incoming. Shawn Dahl (SWPC): couldn't discount "a low-end G5 event." Advance warning 1–2 days before impact.
02
May 10–11, 2024: CMEs arrive. G5 conditions confirmed — first G5 since October 2003. Kp=9, Ap=271, Dst=−412 nT. Solar wind speed 750–950 km/s. Aurora borealis visible across Northern Hemisphere including Texas, Florida, Northern California, Alabama — far south of normal range. Southern Lights visible in New Zealand and Australia. NASA, FAA, FEMA, NERC all notified and prepared. Grid operators on alert with protective procedures ready.
03
May 10–13: No major power grid outages reported in North America. No widespread transformer damage. GPS disruptions minor and temporary. Some radio frequency disruptions. The NOAA warning — "some grid systems may experience complete collapse or blackouts" — did not materialize. Comparison with 2003 Halloween storms: 2003 produced South Africa transformer damage and Sweden blackout. 2024 G5: no equivalent infrastructure damage reported in developed-world grids. The hardening investments held.
04
Post-May 2024: "The most powerful solar storm in history occurred in 1859 — this one also classified as G5" (Texas Tech). Futura Sciences (2026): "The most powerful solar storm since 2003 just hit Earth — and we mostly got off easy." NOAA's warning system worked. Grid operators used advance warning effectively. GIC protections held. Solar Cycle 25 continues toward maximum expected ~2025. The test was real. The preparation worked. The larger test (Carrington-class) has not yet come.
What Worked — and What It Means
Why 2024 was different from 1989
The changes made after 1989 — relay sensitivity adjustments, NERC TPL-007 standards, transformer neutral blocking devices, GIC real-time monitoring — represent 35 years of accumulated engineering investment in making the grid more resilient to the specific mechanism (GICs) that caused the Quebec blackout. The 2024 G5 storm was the first significant test of those protections at a comparable storm intensity. The test result: the protections held. This is the positive case study in the solar flare series — the documentation that the known fix works when applied. The 1989 blackout was a wake-up call. 2024 is evidence that the call was at least partially heeded.
The key operational difference between 1989 and 2024 was advance warning. The 1989 storm struck at 2:44 AM with no significant warning time for grid operators. The 2024 storm was forecast 1–2 days in advance by NOAA's SWPC, notified to NERC and utility operators, and responded to with prepared protective measures. This warning time — enabled by the DSCOVR satellite at L1 and the GOES solar instruments — allowed operators to reduce grid loading, prepare reactive power resources, activate GIC monitoring, and be ready to take immediate protective action when the storm arrived. The warning system is itself a product of post-1989 investment.
What 2024 doesn't prove
The 2024 storm's Dst of −412 nT compares to the 1989 storm's estimated Dst of approximately −600 nT and the 1859 Carrington Event's estimated Dst of −850 nT or more. The 2024 result demonstrates that current grid protections handle a G5 at 2024 intensity well. It does not demonstrate that they would handle a 1989-level event, and certainly not a Carrington-level event, with equivalent success. The FERC and NERC standards that drove post-1989 improvements are calibrated to events of approximately 1989 magnitude. Hardening against a Carrington-class event requires additional investment beyond current standards. Futura Sciences' characterization is accurate: "we mostly got off easy."
The May 2024 storm occurred as Solar Cycle 25 was approaching its maximum — which Texas Tech researchers cited as expected in summer 2025. The 11-year solar cycle peak is when the most powerful flares and CMEs are most likely. The period following a storm like May 2024 is not a period of reduced risk — it is part of the highest-risk window of the solar cycle. Solar Cycle 25 produced the 2024 G5 storm. It may produce larger events before it declines. Maintaining NOAA SWPC monitoring and grid operator preparedness through the full solar maximum period (approximately 2024–2026) is the operational continuity the 2024 success requires.
The cascade lesson
The May 2024 G5 storm is the positive case study in the solar flare series. It documents that the specific lessons of 1989 — relay sensitivity adjustment, GIC monitoring, NERC reliability standards, advance warning — produced measurable protective results when tested at G5 intensity in 2024. The northern lights in Texas were beautiful. The power stayed on. These two facts are connected: the advance warning from NOAA enabled grid operators to prepare, and the GIC protections built after 1989 allowed the grid to absorb the geomagnetic induced currents without cascading failures. For individual household preparedness, the May 2024 result does not mean solar weather risk is resolved. It means the risk is being managed, the management is working for events of current magnitude, and the monitoring and warning infrastructure that makes that management possible needs to be maintained and funded. The 2024 storm was not the Carrington Event. That one will arrive in some future solar cycle — arriving with the same beautiful aurora, the same invisible GICs, and the same question of whether the grid was hardened enough in the intervening years.
What You Can Do Now
The 2024 storm showed that the system works — and provided a practical preview of what individual household preparedness for a major solar weather event looks like. These five actions apply both the positive lesson and its important qualifications.
The 1–2 day advance warning NOAA provided before the May 2024 G5 arrival is genuine, actionable warning time. Bookmarking swpc.noaa.gov and knowing how to read the G-scale storm forecast gives you the same advance information that utility operators, airlines, and military agencies use to prepare. A G4 or G5 watch is the signal to take the same preparation steps as a major storm warning: charge all devices, top off the gas tank, secure your 72-hour supplies, and be ready for a potential outage.
Space weather alert guideThe aurora borealis visible in Texas and Florida during the May 2024 storm is the same phenomenon as the Northern Lights in Quebec during the 1989 storm — intense enough auroras extending to much lower latitudes than normal. If you see the Northern (or Southern) Lights at latitudes where they are normally invisible, a major geomagnetic storm is in progress. This visual indicator tells you to take the same precautions as a G4/G5 storm watch: your grid may be at elevated risk, your GPS may be disrupted, and radio communications may be degraded.
Aurora and storm intensity guideThe 2024 G5 storm was approximately half the magnitude of the 1989 Quebec storm and well below Carrington-level intensity. The grid held because of investments made after 1989, not because the storm was mild. A 1989-scale event would test those protections more severely. A Carrington-scale event would be a qualitatively different scenario. The appropriate takeaway from May 2024 is "the system works at this storm level" — not "we don't need to worry about solar storms anymore."
Solar storm risk guideThe 2024 storm produced NOAA's most severe geomagnetic storm warning in 20 years and no major outage. A future G5 storm might produce the same warning and a significant outage. Maintaining 72 hours of food, water, and essential supplies — and taking preparation steps when a G4/G5 watch is issued — means you are prepared for the event where the grid doesn't hold, at the cost of some extra preparation time for the events where it does. The 2024 storm is the preview of what a major solar event looks like with advance warning. Use that preview to practice your preparation protocol.
72-hour preparedness guideThe advance warning that protected the grid in 2024 came from NOAA's SWPC and from the monitoring satellites (DSCOVR, GOES) that feed it. This infrastructure requires sustained funding and periodic hardware refreshes — the DSCOVR satellite was launched in 2015 and the ACE satellite it supplements dates from 1997. The ESA's SWARM and the planned Lagrange missions represent international investment in improving the warning window. The space weather monitoring infrastructure is public safety infrastructure that works, that has proven its value in the 2024 storm, and that requires sustained investment to maintain its effectiveness for the larger events it hasn't yet had to handle.
Advocacy and public infrastructure guideSolar flare case study series
The Carrington Event 1859 covers the most powerful storm in recorded history. Quebec 1989 covers grid collapse in 92 seconds. Halloween 2003 covers the largest flare ever measured. May 1967 covers the solar storm that nearly triggered a nuclear war. Together, they document the full range of solar weather risk and response.
Full solar flare case study seriesSources