The realistic picture
An extreme geomagnetic storm can induce currents in high-voltage lines and damage transformers, causing regional blackouts. In March 1989, a storm left millions of people in Quebec without power for about nine hours. It can also disrupt GPS, satellite communications and shortwave radio. In May 2024, the strongest storm in two decades produced auroras across much of Europe and North America, without major blackouts.
What won't happen
A solar storm isn't a nuclear electromagnetic pulse. Your phone, laptop or car won't break just from being on: the risk is in long networks such as the power grid. You don't need to keep your devices in a Faraday cage.
Days of warning
The coronal mass ejections behind strong storms usually take one to three days to reach Earth, and space weather centers issue alerts when they happen. That's enough time to check your supplies.
How to prepare
- Prepare as for a long power outage: water, food, light, heat and medication.
- Navigation without GPS: a paper map of your area and a compass.
- Cash, because payments and ATMs depend on the grid.
- An AM/FM radio: local radio usually keeps working.
- A surge protector for expensive devices, also useful in ordinary storms.