How Far South Did the Aurora Reach This Year?

Whether the northern lights are visible from where you live comes down to one number: Kp, the planetary geomagnetic index that runs 0 to 9. NOAA turns Kp into the G-scale storm alerts you see in the news, and the higher it climbs, the further from the poles the aurora slides. We pulled a full year of official Kp readings — every three hours, 2,921 in all — and reduced them to a single chart and one question: over the last twelve months, how far south did the lights actually get within reach?

August 22, 2026  ·  6 min read  ·  all numbers from official NOAA/GFZ Kp data

A Year of Kp

Daily-maximum Kp, 2025-08-22 → 2026-08-22

Each bar is the highest Kp reached on that UTC day. The quiet stretches are real — most nights the aurora stays penned near the Arctic Circle — but storms cluster, and when one lands it can dominate a couple of nights running. The two red bars (November 12, 2025 and January 19, 2026) are the year's G4 peaks; each was flanked by a G3 day as the storm wound down.

What Each Storm Level Means for Where You Live

NOAA publishes an equatorward extent for every G level — the rough southern limit at which the aurora may be seen, low on the horizon, under clear dark skies. The year reached G4, so four of these five rows were live at some point in the last twelve months. (Viewing is never guaranteed: it needs darkness, clear skies away from city light, and a clear view north.)

Southern-extent examples are NOAA's, from the NOAA Space Weather Scales. The single G5 (extreme) row — Florida and southern Texas — was not reached this year; the strongest storms topped out at G4.

Where the Numbers Come From

Kp is a planetary average of geomagnetic disturbance, computed every three hours from a network of magnetometer observatories and issued as the definitive index by the GFZ German Research Centre for Geosciences in Potsdam. It's the same index NOAA's Space Weather Prediction Center watches to issue its G-scale alerts. Twelve months is 2,921 three-hour readings; for the chart above we collapse them to one number per day — that day's maximum — because a single G4 spike at 2 a.m. is what an aurora chaser cares about, not the daily mean.

A caveat worth stating: Kp tells you the aurora is energetic enough to slide toward your latitude, not that you'll see it. Cloud, moonlight, city glow, and whether it's even dark all decide the rest. Kp is the necessary condition — the one you can forecast days ahead — which is why every aurora tool, ours included, is built on it.

Reproduce This

Every figure on this page comes straight from GFZ's public Kp service — no key, no sign-up. Paste this into any terminal with Node 18+ to re-derive the peak, the storm-night count, and the G3+ count for the same window (numbers will extend as new data lands).

// A year of planetary Kp from GFZ Potsdam — the definitive index.
const url = 'https://kp.gfz.de/app/json/?start=2025-08-22T00:00:00Z'
          + '&end=2026-08-22T00:00:00Z&index=Kp';
const { Kp, datetime } = await (await fetch(url)).json();

const rows = datetime.map((t, i) => [t, Kp[i]]).filter(([, k]) => k >= 0);
const peak = Math.max(...rows.map(([, k]) => k));
const stormNights = new Set(rows.filter(([, k]) => k >= 5).map(([t]) => t.slice(0, 10))).size;
const strongNights = new Set(rows.filter(([, k]) => k >= 7).map(([t]) => t.slice(0, 10))).size;

console.log({ readings: rows.length, peakKp: peak, stormNights, strongNights });
// → { readings: 2921, peakKp: 8.67, stormNights: 62, strongNights: 9 }

Related reading: what's worth opening when something's happening overhead, in Live Space Data in Your Browser; and a running count of quakes, storms and asteroids in Planet & Sky Live.

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