Can I see the northern lights tonight in Johnstown?
Unlikely tonight.
NOAA's forecast peaks at Kp 3 during Johnstown's dark hours tonight (6:10 pm to 5:50 am), strongest from about 1:00 am. From Johnstown the aurora usually needs about Kp 7 to show low on the northern horizon and Kp 9 to be overhead. The Moon is 17% lit and up for 23% of the dark hours.
The next three nights
Peak Kp 3 in the dark, 6:10 pm–5:50 am. Moon 17% lit.
Peak Kp 3.67 in the dark, 6:10 pm–6:00 am. Moon 10% lit.
Peak Kp 5 (G1) in the dark, 6:10 pm–6:00 am. Moon 5% lit.
Kp forecast for Johnstown
NOAA planetary K-index: the past day observed, the next three days forecast, in Johnstown local time. Lines: the Kp at which the aurora usually reaches Johnstown's northern horizon, and overhead. The peak value is NOAA's estimated Kp for the 3-hour block starting 1:00 am.
It is dark in Johnstown now. Little aurora activity near you right now.
Seeing the aurora from Johnstown
Johnstown is at 40.3°N, which is magnetic latitude 49.3°: 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 7 it usually reaches low over Johnstown's northern horizon, and at Kp 9 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 Johnstown?
Unlikely. NOAA's forecast peaks at Kp 3 during Johnstown's dark hours tonight (6:10 pm to 5:50 am), strongest from about 1:00 am. From Johnstown the aurora usually needs about Kp 7 to show low on the northern horizon and Kp 9 to be overhead. The Moon is 17% 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 Johnstown?
About Kp 7 to see the aurora low on the northern horizon, and Kp 9 for it to be overhead. Johnstown is at magnetic latitude 49.3°; 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 Johnstown 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 Pennsylvania →Also over Johnstown
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.