How much warning do you get before a geomagnetic storm?

NOAA's Space Weather Prediction Center can issue a Geomagnetic Storm Watch up to 72 hours in advance based on the speed of an observed coronal mass ejection. A Geomagnetic Storm Warning, issued once the disturbance reaches upstream solar wind sensors, typically gives minutes to a couple of hours of more precise notice.

What is the NOAA G-scale for geomagnetic storms?

The G-scale runs from G1 (Minor) to G5 (Extreme) and describes the severity of a geomagnetic storm's effects on power grids, satellites, GPS, and radio communication. Most storms that reach Earth fall in the G1 to G2 range.

Can a geomagnetic storm actually cause a blackout?

Yes, though it is uncommon. A severe geomagnetic storm in March 1989 induced currents strong enough to collapse the power grid serving Quebec for about nine hours. NOAA now works with utility companies to forecast these storms so operators can take protective action before conditions peak.

Will my phone or GPS stop working during a solar storm?

Most storms cause degraded GPS accuracy and occasional HF radio interference rather than a full loss of service. Effects are strongest at high latitudes. Keeping a paper map as backup for driving is a reasonable precaution during a forecast G3 or higher storm.

Is it safe to be outside during a geomagnetic storm?

Yes. A geomagnetic storm poses no direct danger to people on the ground. The visible aurora it produces is a harmless, and often striking, side effect. The storm's real-world impacts are on power grids, satellites, GPS, and radio systems, not on personal safety outdoors.

Solar Flare and Geomagnetic Storm Checklist — Before, During & After

Phase 1

Before a geomagnetic storm. Protect the electronics you rely on.

NOAA's Space Weather Prediction Center forecasts these storms days in advance, similar to how the National Weather Service forecasts a hurricane. The preparation is less about the sky and more about protecting the systems on the ground.

Power

Keep spare batteries stocked and grouped by size for flashlights and radios
Get a portable power station (200 to 400 Wh) that can run small appliances, lighting, and medical devices for days
If you own a generator, test it and review placement rules: outdoors only, at least 20 feet from the house, exhaust pointed away, never in a garage or on a porch
Put surge protectors on major electronics. Geomagnetic storms can induce voltage fluctuations in the grid
Get a power bank for each phone in your household
Get LED lanterns or flashlights for every main room

Financial

Keep $200 to $500 in small bills at home. Card readers and networked payment systems can be affected by grid fluctuations

Documents

Get a waterproof, fireproof container for document copies, plus offline digital backups

Communications

Turn on Wireless Emergency Alerts on every phone in your household
Get a battery-powered or hand-crank NOAA weather radio for when satellite or cell service is degraded

Evacuation

Establish a fuel plan: keep your vehicle's tank at least half full, since GPS navigation may be less reliable during a storm

Water

Store 1 gallon per person per day for at least 3 days, including pets

Food

Build a 3-day supply of shelf-stable food per person that needs no cooking

Phase 2

During a geomagnetic storm. Charge ahead, expect fluctuations, not danger.

A geomagnetic storm poses no direct danger to people. The real effects show up in electronics, navigation, and the power grid, and most households never notice anything beyond a flicker.

If a Storm Watch Is Issued

Charge phones, power banks, and any portable power station fully before the storm's forecast arrival
Back up anything you cannot afford to lose. Fluctuating power can be harder on electronics than a clean outage
Keep your NOAA weather radio or a battery radio ready in case cell and satellite service becomes unreliable

During Active Conditions

Expect GPS and navigation apps to be less accurate. Keep a paper map as backup for driving
Expect HF radio and some satellite communication to be degraded, especially at high latitudes
If you notice the aurora farther south than usual, that is a visible, harmless side effect, not a danger sign

Phase 3

After a geomagnetic storm. Confirm your systems settled back down.

Most fluctuation-related effects resolve on their own once a storm passes. A quick check confirms everything came back the way it should.

Checking Your Systems

Check that sensitive electronics and surge-protected equipment powered back up normally
Confirm GPS and navigation accuracy has returned to normal before relying on it fully
Reset any devices that behaved unusually. Most fluctuation-related issues resolve once the storm passes

Staying Ahead of the Next One

Sign up for NOAA Space Weather Prediction Center alerts if you rely on GPS, HF radio, or off-grid power
Review how your household's surge protection performed, and upgrade it if anything was affected
Keep your portable power station and battery bank charged and ready for the next storm watch

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Solar Flare and Geomagnetic Storm Checklist. Before, during, and after.