Earth is currently at or near the peak of Solar Cycle 25, which means solar flares are more frequent and more powerful than they’ve been in years. An international panel convened by NOAA, NASA, and the International Space Environmental Services predicted this cycle would peak around July 2025, with the window of maximum activity stretching from late 2024 through early 2026. That doesn’t mean a single catastrophic event is coming on a specific date. It means the odds of strong solar flares and geomagnetic storms are elevated throughout this period, and the effects on Earth range from minor inconveniences to, in rare worst-case scenarios, serious infrastructure disruption.
What Solar Maximum Means for 2025
The sun follows an roughly 11-year cycle of activity. During solar maximum, sunspots multiply, and the sun produces more flares and coronal mass ejections (massive clouds of charged particles hurled into space). When those particles reach Earth, they interact with our magnetic field and can trigger geomagnetic storms.
The predicted peak intensity for Cycle 25 is moderate by historical standards, with an expected sunspot number around 115 (the panel’s range was 105 to 125). For comparison, the strongest cycles on record have reached sunspot numbers above 200. So while 2025 is an active year, it’s not expected to be historically extreme. That said, even moderate cycles can produce individual flares powerful enough to cause real problems.
Power Grid Disruptions
The most consequential risk from a strong solar storm is damage to electrical infrastructure. When a geomagnetic storm hits, it causes slow-moving electrical currents to flow through the ground and into anything conductive connected to it, including power lines. These geomagnetically induced currents (GICs) push high-voltage transformers outside their designed operating range. The transformer’s magnetic core becomes saturated, which means it stops providing its normal electrical resistance. Currents and voltages in the windings spike abnormally high, generating intense heat that can physically damage the transformer.
Beyond direct damage, saturated transformers distort the normal 60-cycle electrical signal, which can trick protective equipment elsewhere in the grid into shutting down lines that don’t actually need to be shut down. This cascading effect is what turns a localized problem into a regional blackout. NOAA rates geomagnetic storms on a G1 to G5 scale. At G1 (minor), you get weak grid fluctuations. At G3 (strong), utilities may need to make voltage corrections and deal with false alarms on protection systems. At G5 (extreme), widespread voltage control failures can occur, entire grid sections can collapse, and transformers may sustain permanent damage.
Utilities have been preparing. One key defense is neutral blocking devices: capacitors installed on transformer grounding paths that prevent GICs from flowing through the windings. These were designed specifically to counter geomagnetic storms. Grid operators also have real-time monitoring from NOAA’s Space Weather Prediction Center, giving them minutes to hours of warning to take protective measures like reducing load on vulnerable transformers.
Satellite and GPS Problems
Satellites are more exposed than anything on the ground because they sit above Earth’s protective atmosphere. During strong storms, satellites can accumulate electrical charge on their surfaces, causing electronic malfunctions. Orientation systems can lose track of position, and communication links between ground stations and satellites can degrade. At G5 levels, NOAA warns of “extensive surface charging” and problems with tracking, uploading commands, and downloading data.
There’s also a subtler effect: solar activity heats Earth’s upper atmosphere, causing it to expand. This increases drag on satellites in low orbit, pulling them downward faster than expected. Operators have to burn fuel to boost orbits more frequently, shortening satellite lifespans. SpaceX lost about 40 Starlink satellites in early 2022 to exactly this kind of atmospheric drag after a moderate geomagnetic storm.
GPS accuracy suffers too. Solar flares alter the density of the ionosphere, which GPS signals pass through on their way to your phone. Those density changes introduce positioning errors. During severe storms, satellite navigation can be degraded for hours or even days. This matters most for precision applications like aviation approaches, surveying, and autonomous systems, though everyday phone navigation may also show unusual inaccuracies.
Radio Blackouts
High-frequency (HF) radio, which operates between 1 and 30 megahertz, is particularly vulnerable. Airlines, military operations, emergency services, and amateur radio operators all rely on these frequencies. When X-rays from a solar flare hit Earth’s upper atmosphere, they create a dense layer of ionization that absorbs HF signals instead of bouncing them back to the ground.
These blackouts happen on the sunlit side of Earth and are most intense when the sun is directly overhead. They typically last minutes to hours for a single flare. During a G5 storm, HF radio can be completely unusable across large regions for one to two days. Polar flight routes are especially affected because high-energy protons from solar storms funnel toward the poles along Earth’s magnetic field lines, creating additional radio absorption in exactly the areas where transoceanic flights need communication most.
Radiation Exposure for Air Travelers
At cruising altitude, you’re above much of the atmosphere’s protective shielding. During solar particle events, radiation doses on flights increase measurably. A study of flight attendant exposure found that individual flight segments during solar storms delivered doses as high as 1.2 millisieverts, compared to typical segment averages well under 0.02 millisieverts. Twenty flight segments in the study exceeded 0.5 millisieverts each.
For an occasional flyer, this is not a meaningful health risk. For pregnant flight crew, it’s more significant: a single high-dose flight segment during a solar storm could potentially exceed the recommended monthly limit for fetal exposure of 0.5 millisieverts. Airlines reroute flights away from polar paths and to lower altitudes during major solar events partly for this reason, and partly because of the radio blackout issues at high latitudes.
Will Your Phone or Computer Be Damaged?
This is one of the most common fears, and the short answer is no. Consumer electronics on the ground are not directly at risk from solar flares. Your phone, laptop, and home appliances are too small to act as antennas for geomagnetically induced currents, which need very long conductors (think hundreds of miles of power line or pipeline) to build up dangerous voltage. The U.S. Geological Survey notes that the real danger is to large-scale infrastructure: power grids, satellites, and navigation systems. Your devices would only be affected indirectly, through power outages or degraded cell and internet service that depend on those larger systems.
How Bad Could It Really Get?
The benchmark for a worst-case scenario is the 1859 Carrington Event, the largest recorded geomagnetic storm. It produced magnetic field disturbances estimated between 850 and 1,760 nanoteslas (for reference, even G5 storms in modern times rarely exceed 500). Telegraph systems across North America and Europe failed, with some operators reporting electric shocks and equipment catching fire.
If a Carrington-scale event happened today, the USGS warns that cascading failures across satellites, navigation systems, and power grids could cause regional blackouts lasting not hours but potentially weeks, since replacing damaged high-voltage transformers takes months. The interconnected nature of modern infrastructure means one failure can ripple across systems in ways that weren’t possible in 1859. A 2019 study in Scientific Reports estimated the probability of a Carrington-class storm, and while such events are rare in any given year, the elevated activity of solar maximum increases the odds.
The most likely outcome for 2025, though, is far less dramatic. Expect occasional G2 or G3 storms producing minor grid fluctuations, sporadic GPS degradation, some HF radio interruptions, and spectacular aurora visible much farther south than usual. At G2, aurora can be seen as far south as New York and Idaho. At G3, as far as Illinois and Oregon. At G5, people in Florida and southern Texas have historically seen the northern lights.
How You’ll Be Warned
NOAA’s Space Weather Prediction Center monitors the sun continuously and issues alerts on the same G1 through G5 scale used for the impacts above. Warnings for geomagnetic storms can come hours to days before impact, since coronal mass ejections take one to three days to travel from the sun to Earth. Flare-driven radio blackouts, by contrast, arrive at the speed of light and hit with only about eight minutes of notice. NOAA publishes forecasts, watches, and real-time storm data at spaceweather.gov, and many weather apps now include space weather alerts.