Northern Lights Tonight

It depends on three things: how active the geomagnetic field is, how close you are to the auroral zone, and whether your sky is dark and clear. The verdict at the top of this page combines NOAA's live Kp index and its forecast for the next 24 hours with the approximate latitude the aurora reaches at that level. If your area is listed as a good chance, get away from city lights and look toward the poleward horizon (north in the Northern Hemisphere, south in the Southern Hemisphere) from late evening into the early hours.

Kp is NOAA's planetary index of geomagnetic activity, on a scale from 0 to 9 in three-hour blocks. It is published in thirds, so 3.67 means "4 minus". The higher the number, the brighter the aurora and the farther it spreads from the poles: as a rule of thumb from NOAA, the edge of the auroral oval moves about 2 degrees of geomagnetic latitude toward the equator for each step. Kp 5 and above is a geomagnetic storm on NOAA's G scale, from G1 (minor) at Kp 5 to G5 (extreme) at Kp 9.

Roughly: almost any Kp in Alaska, northern Canada, Greenland, Iceland and northern Scandinavia; about Kp 3 in the Faroe Islands; about Kp 4 in southern Canada, Shetland and southern Finland; about Kp 5 in the northern tier of U.S. states and southern Scandinavia; about Kp 6 in the Great Lakes, the Pacific Northwest, Scotland, Denmark, the south of New Zealand and Tasmania; about Kp 7 in New England, Ireland, northern England, northern Germany and the rest of New Zealand; about Kp 8 in the central U.S., the Mid-Atlantic, the Netherlands, southern England and Victoria; and about Kp 9 in central Europe. Closer to the equator than that it takes a rare, extreme storm. These are averages from NOAA's guidance, and a real night can beat them or fall short.

NOAA's advice is that the best aurora is usually within an hour or two of local midnight, roughly 10 p.m. to 2 a.m., and that the window widens toward evening and morning as activity rises. It also has to be properly dark: this page counts a place as dark when the sun is more than 12 degrees below its horizon. Close to the poles that never happens in summer, which is why aurora season in places like Alaska, Iceland and northern Norway runs roughly from late August to mid-April.

The aurora glows about 100 km (60 mi) and more above the ground, far above the weather, so any cloud between you and it hides it completely: a clear sky matters as much as a high Kp. A bright moon, like city lights, does not change the aurora itself but washes out its fainter parts, so dark nights around the new moon, away from towns, show the most. A strong display is still easy to see under a full moon.

Under the auroral oval, which sits over roughly the same band every night: northern Norway, Sweden and Finland (Tromsø, Abisko, Rovaniemi), Iceland, Alaska (Fairbanks), northern Canada (Yellowknife, Whitehorse) and Greenland. There, even a quiet night with Kp 2 or 3 often puts on a show. Pick a spot with a clear, dark view toward the pole (a hilltop or a lake shore works well). In the Southern Hemisphere the aurora australis is seen most often from Tasmania, the south of New Zealand's South Island and Antarctica.

Yes, on the right night. A camera needs a dark sky, a view toward the pole and a sensor that copes with faint light. Many webcams are tuned for daytime, so a weak aurora may show as little more than a green tint while a strong one is obvious. The chance on each webcam card is NOAA's OVATION estimate of aurora overhead at that spot right now, and the dark badge means the sun is more than 12 degrees below the horizon there. Cameras in the Southern Hemisphere can catch the aurora australis.

The OVATION map is a short-term forecast driven by the solar wind measured by spacecraft about 1.5 million km (930,000 mi) upstream of Earth, so it is best for the next 30 to 90 minutes. The 3-day Kp forecast is less certain, because the arrival time and strength of an eruption from the sun can be off by many hours. NOAA's Kp to latitude guidance is an average too: use it as a rule of thumb, then check the sky.