Northern lights forecast tonight

What the aurora is

The aurora is light given off high in the atmosphere when electrons, driven down Earth’s magnetic field by the solar wind, strike oxygen and nitrogen. NOAA explains that the glow starts around 60 miles (100 km) up. The common green comes from oxygen, deep red from oxygen even higher up, and purple from nitrogen lower down. The biggest displays follow coronal mass ejections, clouds of solar material that hit Earth’s magnetic field.

Kp and the G-scale

Kp is NOAA’s 0–9 index of how disturbed Earth’s magnetic field is. Each value covers three hours and is built from magnetometer readings around the world. A value of 5 or more counts as a geomagnetic storm. NOAA’s G-scale then gives storms a name: Kp 5 is G1 (minor), 6 is G2 (moderate), 7 is G3 (strong), 8 is G4 (severe) and 9 is G5 (extreme).

The higher the level, the farther the aurora reaches toward the equator. According to NOAA’s scale, minor storms are commonly seen in northern Michigan and Maine. Moderate storms reach New York and Idaho, and strong storms reach Illinois and Oregon. Severe storms have reached Alabama and northern California, and extreme storms Florida and southern Texas. The scale also counts how often each level comes: minor storms happen on hundreds of days per 11-year solar cycle, extreme ones on only a handful.

How our state and city levels work

The aurora follows Earth’s magnetic field, not the map grid, so we convert each city to geomagnetic latitude. We then read off, interpolating between levels, the Kp at which NOAA’s scale puts the aurora’s visible edge at that latitude. That is the level shown for each state and city, and it is compared with NOAA’s live Kp forecast for tonight. North of about 60° geomagnetic latitude, which covers much of Alaska, the aurora can be overhead even on quiet nights, so the levels there are much lower. Details are on our methodology page.

“Possible tonight” means the highest Kp in NOAA’s forecast for tonight’s dark hours reaches your level, so the aurora may be visible low on your northern horizon from a dark spot. “Camera only, maybe” means the forecast falls within one level of it, close enough that a phone camera may record a glow your eyes can’t see. Neither is a promise: clouds, moonlight and city glow all decide what you actually see, and forecasts more than a day ahead are uncertain.

Why cameras see more than eyes

At night the eye picks out brightness before color, so a faint aurora can look like a pale gray cloud. NOAA notes that the eye sees the aurora’s true colors only when it is fairly bright, and that digital cameras can record the aurora and its colors when it is too dim for people to see. If a “cloud” to the north turns green or pink in a photo, you are probably looking at the aurora.

Best times of night and year

NOAA says the aurora is usually best within an hour or two of midnight. During strong storms it can start at dusk and last until dawn.

NOAA also says bigger storms tend to come near the spring and fall equinoxes. The University of Alaska Fairbanks Geophysical Institute calls this the Russell-McPherron effect and puts the odds of seeing aurora over Interior Alaska at about twice as high at the equinoxes as at the solstices.

You still need darkness: the institute gives Fairbanks a viewing season of roughly August 21 to April 21, because summer skies there never get dark enough. Farther south, summer nights are dark but short.

For a step-by-step plan, read how to see the northern lights.