What G level do I need to see the northern lights?

It depends on your geomagnetic latitude. The far-north towns on Glow sit under the average oval edge at G1. Duluth needs G2, and the other lower 48 towns G3, by SWPC's edge rule.

What is the difference between Kp and G?

Kp is the planetary index from 0 to 9. The G-scale renames the storm range of Kp: G1 is Kp 5 up to G5 at Kp 9.

How often do G5 storms happen?

SWPC lists 4 per 11-year cycle, on 4 days.

Where can a G3 storm be seen?

SWPC says aurora has been seen as low as Illinois and Oregon, typically 50 degrees geomagnetic.

Does a higher G level mean brighter aurora?

SWPC's tips page says the aurora becomes brighter and more active at higher Kp, and moves farther from the poles.

NOAA Space Weather Scales

Geomagnetic storm levels and the aurora

Answer

NOAA grades geomagnetic storms from G1 Minor (Kp 5) to G5 Extreme (Kp 9). For each level SWPC lists where aurora has been seen, from northern Michigan and Maine at G1 to Florida and southern Texas at G5, and how often it happens per 11-year solar cycle.

G1 to G5

Kp 5 to 9

The scale at a glance

NOAA G-scale with SWPC's aurora reach, frequency and the Glow towns at or poleward of each level
Level	Kp	Aurora seen as low as	Per cycle	Days a year	Oval edge	Towns reached
G1 Minor	Kp = 5	aurora is commonly visible at high latitudes (northern Michigan and Maine)	1,700	82	56°	5 of 10
G2 Moderate	Kp = 6	aurora has been seen as low as New York and Idaho (typically 55° geomagnetic lat.)	600	33	54°	6 of 10
G3 Strong	Kp = 7	aurora has been seen as low as Illinois and Oregon (typically 50° geomagnetic lat.)	200	12	52°	10 of 10
G4 Severe	Kp = 8, including a 9-	aurora has been seen as low as Alabama and northern California (typically 45° geomagnetic lat.)	100	5.5	50°	10 of 10
G5 Extreme	Kp = 9	aurora has been seen as low as Florida and southern Texas (typically 40° geomagnetic lat.)	4	0.4	48°	10 of 10

Aurora column quoted from the NOAA scales page. Days a year: days per cycle divided by 11. Oval edge: SWPC's 66 minus 2 per Kp rule in geomagnetic latitude. Towns reached: Glow towns at or poleward of that edge on the IGRF-14 dipole.

How the scale works

The G-scale is one of three NOAA Space Weather Scales, and it rests on the planetary Kp index. SWPC counts Kp 5 or more as a geomagnetic storm, so the scale starts there: Kp 5 is G1, Kp 6 is G2, Kp 7 is G3, Kp 8 (including a 9-) is G4 and Kp 9 is G5. Each step describes effects on power systems, spacecraft and radio as well as the aurora; Glow quotes only the aurora column.

The frequency column counts storms per 11-year solar cycle. Lower levels are far more common. G1 comes about 1700 times per cycle, G3 about 200 and G5 about 4. Glow divides by 11 to give a yearly average, but storms are not spread evenly across a cycle.

The aurora column names places and, from G2 up, a typical geomagnetic latitude: 55, 50, 45 and 40 degrees. Those describe where people have seen aurora, not where the aurora itself is. SWPC makes that distinction on its tips page.

Sighting latitude and oval edge

"At Kp = 0, the equator ward edge of the auroral oval is approximately 66 degrees. And it moves equatorward about 2 degrees for each level of Kp."
NOAA SWPC, Tips on viewing the aurora

SWPC gives a second rule on its tips page: the oval's equatorward edge sits near 66 degrees at Kp 0 and moves about 2 degrees per Kp step. At G5, Kp 9, that puts the edge at 48 degrees, while the scale lists sightings down to 40. The 8-degree gap, about 890 km, is viewing distance: SWPC says bright aurora can be seen from as far as 1000 km away.

Glow shows both rules for every level. The typical latitude answers "has anyone at my latitude seen it at this level?" The edge rule answers "is the oval itself likely overhead?" For your own coordinates, the Kp needed tool runs both, and the Kp to latitude chart explains the conversion.

Using storm levels to plan

SWPC issues watches for the G level predicted for a coming day, and alerts when Kp reaches a level. For the far-north towns on Glow, even G1 puts the average oval edge overhead. For Duluth it takes G2. For Minneapolis, Seattle, Buffalo and Portland, Maine it takes G3, though aurora on the northern horizon is possible a level or two earlier.

Once a storm is under way, switch from the level to the live map. The oval map and the southern edge tool show where the oval actually sits, which Kp only estimates. The alerts guide lists the Kp thresholds behind each SWPC product.

Questions

What G level do I need to see the northern lights?: It depends on your geomagnetic latitude. The far-north towns on Glow sit under the average oval edge at G1. Duluth needs G2, and the other lower 48 towns G3, by SWPC's edge rule.
What is the difference between Kp and G?: Kp is the planetary index from 0 to 9. The G-scale renames the storm range of Kp: G1 is Kp 5 up to G5 at Kp 9.
How often do G5 storms happen?: SWPC lists 4 per 11-year cycle, on 4 days.
Where can a G3 storm be seen?: SWPC says aurora has been seen as low as Illinois and Oregon, typically 50 degrees geomagnetic.
Does a higher G level mean brighter aurora?: SWPC's tips page says the aurora becomes brighter and more active at higher Kp, and moves farther from the poles.

Sources and verification

NOAA Space Weather Scaleshttps://www.spaceweather.gov/noaa-scales-explanation
NOAA SWPC, Tips on viewing the aurorahttps://www.spaceweather.gov/content/tips-viewing-aurora
NOAA SWPC, Planetary K-indexhttps://www.swpc.noaa.gov/products/planetary-k-index
NOAA SWPC, Aurora 30-minute forecasthttps://www.spaceweather.gov/products/aurora-30-minute-forecast

Quoted figures last checked against their sources on 2026-09-30; next review 2026-12-31. Computed figures come from SunCalc and the IGRF-14 dipole as described in the methodology. Every quote is listed in the sources ledger.