Can I see the northern lights tonight in Sioux City?
Unlikely tonight.
NOAA's forecast peaks at Kp 3 during Sioux City's dark hours tonight (6:20 pm to 6:10 am), strongest from about 12:00 am. From Sioux City the aurora usually needs about Kp 6 to show low on the northern horizon and Kp 8 to be overhead. The Moon is 16% lit and up for 23% of the dark hours.
The next three nights
Peak Kp 3 in the dark, 6:20 pm–6:10 am. Moon 16% lit.
Peak Kp 2.33 in the dark, 6:20 pm–6:10 am. Moon 9% lit.
Peak Kp 5 (G1) in the dark, 6:20 pm–6:10 am. Moon 4% lit.
Kp forecast for Sioux City
NOAA planetary K-index: the past day observed, the next three days forecast, in Sioux City local time. Lines: the Kp at which the aurora usually reaches Sioux City's northern horizon, and overhead. The peak value is NOAA's estimated Kp for the 3-hour block starting 12:00 am.
It is dark in Sioux City now. Little aurora activity near you right now.
Seeing the aurora from Sioux City
Sioux City is at 42.5°N, which is magnetic latitude 51.7°: the aurora follows the magnetic pole, not the geographic one, which is why it reaches further south over North America than over Europe. In a quiet night the auroral oval stays far to the north. When a solar storm arrives the oval widens and slides south; at about Kp 6 it usually reaches low over Sioux City's northern horizon, and at Kp 8 it can be overhead.
Kp forecasts more than a day ahead are uncertain: the timing and strength of a solar storm are often only clear an hour or so before it hits, when it passes the spacecraft upstream of Earth. So a "possible" night can fizzle, and a quiet forecast can surprise. This page updates every 30 minutes. The full week's aurora forecast · What the Kp index means.
Questions
Can I see the northern lights tonight in Sioux City?
Unlikely. NOAA's forecast peaks at Kp 3 during Sioux City's dark hours tonight (6:20 pm to 6:10 am), strongest from about 12:00 am. From Sioux City the aurora usually needs about Kp 6 to show low on the northern horizon and Kp 8 to be overhead. The Moon is 16% lit and up for 23% of the dark hours. You also need clear skies to the north, which we do not forecast.
What Kp do you need to see the northern lights in Sioux City?
About Kp 6 to see the aurora low on the northern horizon, and Kp 8 for it to be overhead. Sioux City is at magnetic latitude 51.7°; the southern edge of the auroral oval sits near 66.5° at Kp 0 and moves about 2° south per Kp step.
What time is best to see the aurora?
Usually within a couple of hours of midnight local time, when your part of the Earth faces the night side of the auroral oval. During a storm it can show any time it is dark, so watch the live Kp and go out when it jumps.
Where should I look?
North. From Sioux City the aurora usually appears as a green or grey glow low over the northern horizon, rising higher only in strong storms. Get away from street lights and let your eyes adjust for 15 minutes. A phone camera on night mode often shows colour the eye cannot.
Northern lights nearby
All of Iowa →Also over Sioux City
Data: NOAA Space Weather Prediction Center (planetary K-index forecast, 3-day forecast, 27-day outlook, OVATION aurora model). Magnetic latitudes: AACGM-v2. Darkness and Moon computed with Skyfield and JPL DE440. We do not forecast clouds: you need a clear view to the north. How the verdict is made.