Your Local Risks · Hazard Guide
The 1859 Carrington Event was the last major geomagnetic storm to hit a wired civilization. Scientists classify another event of that scale as a matter of when, not if. Preparation is straightforward — and overlaps entirely with extended power outage preparedness.
Understanding the hazard
The sun periodically releases massive bursts of charged particles called coronal mass ejections (CMEs). Think of them as enormous pressure waves traveling through space at millions of miles per hour. When a CME strikes Earth's magnetic field, the resulting interaction — called a geomagnetic storm — can induce powerful electrical currents in anything long and conductive on Earth's surface: power lines, pipelines, telegraph wires, undersea cables.
Most geomagnetic storms are minor and produce nothing more than impressive auroras. Significant storms — classified G3 and above on NOAA's scale — can disrupt GPS, communications satellites, and cause localized power grid stress. An extreme storm (G5) can damage large electrical transformers that take months to years to replace, potentially blacking out entire regions for extended periods.
The 1989 Quebec geomagnetic storm provides the clearest modern example: it took down the entire provincial power grid in 90 seconds, leaving 6 million people without electricity for up to nine hours. A Carrington-class storm would be significantly more powerful than the Quebec event.
The risk spectrum
NOAA classifies geomagnetic storms on a G1–G5 scale. What actually happens to your household depends on where on that scale the event falls.
G1
Weak power grid fluctuations. Aurora visible at high latitudes. No household impact expected.
G2
Voltage alerts at high latitudes. HF radio propagation degraded. Transformer heating possible.
G3
Voltage corrections required on power systems. Satellite drag increases. GPS accuracy affected. Aurora at mid-latitudes.
G4
Widespread voltage control problems. Protective devices trip. Some grid systems may experience outages. Pipeline corrosion accelerated.
G5
Complete collapse of some grid systems. Transformer damage. Widespread outages lasting weeks or months. The Carrington Event was estimated at this level.
Source: NOAA Space Weather Prediction Center Geomagnetic Storm Scale
What to do
At the household level, the primary risk of an extreme geomagnetic storm is an extended power outage. The preparation is the same — with a few additional steps for the communication and electronics dimensions.
A G5 event's primary household impact is a multi-week or multi-month power outage. Two weeks of water, food, and backup power is the baseline preparation — the same as any extended outage scenario.
Power outage guide →In an extreme solar event, cell networks and internet infrastructure would likely fail along with the grid. A hand-crank NOAA weather radio is your most resilient information source. A battery-powered AM radio is the backup. Identify your household's communication plan that doesn't depend on cell service.
Banking and card payment infrastructure depends on the grid and communications networks. In an extended solar-event scenario, physical cash, paper copies of key documents, and paper records of account information are the backup financial system for your household.
NOAA's Space Weather Prediction Center issues forecasts and alerts for significant solar activity. G3 and above alerts provide 1–3 days of warning for CME-based events. Signing up for SWPC alerts gives you the earliest possible notification of an approaching extreme storm.
NOAA SWPC alerts →A Faraday cage — a conductive enclosure — can protect electronics stored inside from electromagnetic induction. For most households, this is an optional step; the primary risk is grid-down, not individual device damage. A metal garbage can with a tight-fitting lid works for small electronics.
Extended grid failure affects powered medical equipment, pharmacy operations, and prescription refill systems. The same medical preparedness steps that apply to extended power outages apply here — backup power for critical equipment, prescription buffer, and a plan for medical supply chains.
Official resources
The foundation
Preparing for a geomagnetic storm at the household level is the same as preparing for any extended grid failure. The power outage guide covers the supplies, backup power tiers, and communications plan that make your household resilient for weeks without grid power.
Extended power outage guide