- There is no geomagnetic storm on 27 September 2026; the planetary Kp index peaks at 4.
- A geomagnetic storm begins at Kp 5, which NOAA calls level G1 (minor).
- The geomagnetic field is forecast at Kp 2 on 28 September 2026.
- The Kp index is measured in three-hour intervals on a scale from 0 to 9.
- The NOAA Space Weather Prediction Center publishes the Kp index, a 3-day forecast and a 27-day outlook.
Kp index today, hour by hour
The Kp index is measured in three-hour windows. Bars show observed values; outlined bars are NOAA estimates for the rest of the day.
Geomagnetic storm forecast for 3 days
| Day | Peak Kp | Level | Storm |
|---|---|---|---|
| Today, Sun 27 Sep | 4 | Active | No |
| Tomorrow, Mon 28 Sep | 2 | Quiet | No |
| Tue 29 Sep | 1.7 | Quiet | No |
| Wed 30 Sep | 1.7 | Quiet | No |
Geomagnetic storms in October: the 27-day outlook
The Sun turns once in about 27 days, so active regions come back on schedule. Bars show the largest daily Kp NOAA expects.
What the Kp index and the G scale mean
| Kp | Level | How often | Aurora seen as far south as |
|---|---|---|---|
| 0 to 3 | Quiet to unsettled | Most days | Polar regions only |
| 4 | Active | Several days a month | Northern Scandinavia, Alaska |
| 5 | G1 · minor storm | About 900 days per 11-year cycle | Northern Michigan, Maine |
| 6 | G2 · moderate storm | About 360 days per cycle | New York, Idaho |
| 7 | G3 · strong storm | About 130 days per cycle | Illinois, Oregon |
| 8 | G4 · severe storm | About 60 days per cycle | Alabama, northern California |
| 9 | G5 · extreme storm | About 4 days per cycle | Florida, southern Texas |
How a geomagnetic storm may feel
People who describe themselves as weather-sensitive most often report headaches, poor sleep, tiredness and a quick temper on active days. Many people notice nothing at all.
- Headache and pressure in the head
- Light or broken sleep
- Changes in blood pressure
- Tiredness and irritability
Findings are mixed. Some studies link geomagnetic activity with small shifts in heart rate variability and sleep. Others find no effect. Nothing here is medical advice.
What you can do on active days
Questions people ask
Is there a geomagnetic storm today?
The answer is in the first line of this page and is updated every three hours from NOAA. A storm begins at Kp 5, which is level G1.
Will there be a geomagnetic storm tomorrow?
The 3-day forecast table shows tomorrow’s expected peak Kp. Forecasts beyond three days come from the 27-day outlook and are less certain.
How long does a geomagnetic storm last?
Most storms last from a few hours to a day or two. Storms caused by coronal mass ejections can be longer and stronger than those caused by high-speed solar wind streams.
Can a geomagnetic storm cause headaches?
Some people report headaches on active days, and some studies find small associations. The evidence is mixed, and a headache has many other causes.
What is the difference between a solar flare and a geomagnetic storm?
A solar flare is a burst of light and radiation on the Sun that reaches Earth in about eight minutes. A geomagnetic storm is a disturbance of Earth’s magnetic field, usually one to three days after material leaves the Sun.
Will the northern lights be visible tonight?
The stronger the storm, the further south the aurora is seen. At Kp 5 it reaches northern Scandinavia and Scotland; at Kp 7 central Europe and the northern United States. Clear, dark skies are needed.
When was the last strong geomagnetic storm?
The past-days list on this page links to every day in the archive with its peak Kp, so the last G3 or stronger day can be found there.
- NOAA Space Weather Prediction Center: planetary K index, 3-day forecast, 27-day outlook, space weather scales.
- Alabdulgader A. et al. Long-term study of heart rate variability responses to changes in the solar and geomagnetic environment. Scientific Reports, 2018.
- Palmer S. J., Rycroft M. J., Cermack M. Solar and geomagnetic activity, extremely low frequency magnetic and electric fields and human health at the Earth’s surface. Surveys in Geophysics, 2006.
Numbers update through the day from public sources. The text for each day is written from that day’s data and checked by the editor. Every past day keeps its own page in the archive.