How reliable is the 3-day forecast?
NOAA's Kp prediction is most accurate for the first day and grows less certain with each following day. A sudden Earth-directed CME can change the picture within hours — which is why a daily check is worth it.
Live forecast · NOAA
Solar storm 3-day forecast
The highest expected Kp for the rest of today, tomorrow and the day after — straight from the official NOAA prediction, fresh on every visit. For what has already happened today, see the live dashboard.
Forecast
Maximum Kp per day
Days follow Central European time (Europe/Berlin). Each card shows the expected daily maximum.
Understanding the Kp scale
The Kp index measures how disturbed Earth's magnetic field is worldwide, on a scale from 0 to 9. NOAA's storm scale (G1–G5) begins at Kp 5.
| Kp | NOAA | Level | What it means |
|---|---|---|---|
| 0–2 | G0 | Quiet | No noticeable effects. Auroras only near the poles. |
| 3–4 | G0 | Elevated | Unsettled magnetic field. Auroras possible over northern Scandinavia and Iceland. |
| 5 | G1 | Minor storm | Auroras possible at mid latitudes — e.g. the northern US or northern Germany under clear skies. |
| 6 | G2 | Moderate storm | Clearly visible auroras possible at mid latitudes; occasional HF radio disturbances. |
| 7 | G3 | Strong storm | Auroras far south; satellite navigation and radio can be degraded. |
| 8–9 | G4–G5 | Severe to extreme | Rare. Possible impacts on power grids and satellites; auroras very far south. |
How to read the forecast
NOAA publishes its Kp prediction in 3-hour intervals. We group them per calendar day and show the expected maximum — the most disturbed moment of that day. A day labelled "Kp 4.7" can still be mostly quiet, with just one unsettled window.
The first day of the forecast is the most reliable. If an Earth-directed coronal mass ejection (CME) erupts, the picture can change within hours — the current solar activity of the past 24 hours shows whether something is on the way.
Forecast and wellbeing
Some people follow the forecast because they report headaches, restless sleep or fatigue during geomagnetically disturbed periods. Observational studies show timing associations, not a proven mechanism. Whether these values mean aurora at your latitude is covered on the aurora tonight page.
More in the wellbeing section of the dashboard — data, not diagnoses.
FAQ
Questions about the 3-day forecast
What does Kp 5 mean?
From Kp 5, NOAA classifies conditions as a G1 geomagnetic storm. Auroras become more likely at higher latitudes; notable effects on power grids and satellites only begin around G3–G4 (Kp 7 and above).
When is the next solar storm?
It can only be predicted reliably a few days ahead. This page shows the official 3-day forecast: if the expected maximum rises to Kp 5 or more, a geomagnetic storm is on the schedule.
Where does the data come from?
From NOAA's Space Weather Prediction Center. The page fetches the official Kp prediction fresh on every visit — no caching layer and no reinterpretation of the raw data.