Can you see the northern lights in Pennsylvania tonight?
Unlikely tonight. Kp is 1.00 at 3:37 PM EDT, and Pennsylvania needs about Kp 5 before the aurora reaches its northern horizon.
Kp now
1.00
Pennsylvania needs
Kp 5
Verdict
No chance
Sky tonight
Mostly clear, 24% cloud
Kp from NOAA SWPC estimated planetary K index, read at 3:37 PM EDT. Cloud cover for Cherry Springs State Park from the National Weather Service CTP gridded forecast.
Why Pennsylvania needs Kp 5
The aurora follows the Earth's magnetic field rather than the equator, so what matters is geomagnetic latitude, not the number on a map. The northern edge of Pennsylvania sits at 51.5° geomagnetic. The auroral oval reaches that far south at about Kp 5, allowing for the five degrees of extra reach you get from aurora sitting high in the atmosphere and showing low on the horizon.
Cloud is the usual reason a good Kp night comes to nothing. At Cherry Springs State Park, in the north of the state, tonight is forecast mostly clear at 24% cover, with the clearest hour around 12:00 AM.
The next three days
NOAA's three-hour Kp outlook. The highest expected value is Kp 4.00, which stays below the Kp 5 Pennsylvania needs.
| Day | Window | Kp | In range |
|---|---|---|---|
| Aug 20 | 00-03UT | 2.67 | No |
| Aug 21 | 00-03UT | 4.00 | No |
| Aug 22 | 00-03UT | 3.00 | No |
| Aug 20 | 03-06UT | 2.00 | No |
| Aug 21 | 03-06UT | 2.00 | No |
| Aug 22 | 03-06UT | 4.00 | No |
| Aug 20 | 06-09UT | 2.00 | No |
| Aug 21 | 06-09UT | 1.67 | No |
| Aug 22 | 06-09UT | 2.67 | No |
| Aug 20 | 09-12UT | 2.00 | No |
| Aug 21 | 09-12UT | 2.33 | No |
| Aug 22 | 09-12UT | 2.67 | No |
| Aug 20 | 12-15UT | 2.33 | No |
| Aug 21 | 12-15UT | 2.33 | No |
| Aug 22 | 12-15UT | 2.67 | No |
| Aug 20 | 15-18UT | 2.00 | No |
| Aug 21 | 15-18UT | 2.67 | No |
| Aug 22 | 15-18UT | 2.00 | No |
| Aug 20 | 18-21UT | 2.33 | No |
| Aug 21 | 18-21UT | 2.67 | No |
| Aug 22 | 18-21UT | 1.00 | No |
| Aug 20 | 21-00UT | 3.67 | No |
| Aug 21 | 21-00UT | 3.00 | No |
| Aug 22 | 21-00UT | 2.00 | No |
NOAA SWPC three-day forecast, issued 2026 Aug 20 1215 UTC.
Watching from Pennsylvania
- Look north, low on the horizon. From Pennsylvania the aurora rarely climbs overhead.
- Get away from town lights and give your eyes twenty minutes to adjust.
- The most active hours are usually between 10pm and 2am local time, around magnetic midnight.
- A phone on a three to five second exposure will pick up colour your eyes cannot, so a grey glow to the naked eye can still photograph green.