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SESK: Stuff Everyone Should Know · sesk.info/hame-kp5-g1

On NOAA's scale, a G1 geomagnetic storm begins at what Kp value?

Kp 5.

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  1. Kp 3
  2. Kp 5 ✔
  3. Kp 7

Why: NOAA's K-index runs from 0 to 9, and a value of 5 or higher indicates a geomagnetic storm. G1 (Minor) is Kp 5 and G5 (Extreme) is Kp 9.

Huh, didn't know that: The planetary Kp index averages readings from 13 magnetometer observatories.

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References

Answer: Kp 5. NOAA's K-index runs from 0 to 9, and a value of 5 or higher indicates a geomagnetic storm. G1 (Minor) is Kp 5 and G5 (Extreme) is Kp 9.

  1. NOAA Space Weather Scales www.spaceweather.gov/noaa-scales-explanation
    G 1 | Minor
    Checked 2026-10-11.
  2. NOAA Space Weather Scales www.spaceweather.gov/noaa-scales-explanation
    Kp = 5
    Checked 2026-10-11.
  3. NOAA SWPC Planetary K-index www.spaceweather.gov/products/planetary-k-index
    5 or more indicating a geomagnetic storm
    Checked 2026-10-11.
  4. NOAA SWPC Planetary K-index www.spaceweather.gov/products/planetary-k-index
    from 13 geomagnetic observatories
    Checked 2026-10-11.

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