Pennsylvania · 6 towns compared
Northern lights in Pennsylvania: tonight’s chance
Pennsylvania needs a strong storm everywhere; its northern counties hold some of the darkest skies in the East to make it count.
Tonight at Erie, PA
…
Reading the SWPC Kp forecast and the cloud forecast…
| Kp forecast during the dark hours | not yet forecast |
|---|---|
| Kp needed here | 6.8 (G3 strong) |
| Cloud cover in the dark hours | loading |
| Dark sky (Sun 18° down) | 8:14 PM to 5:58 AM EDT |
| Moon | 13% lit |
| Right now, OVATION (30 to 90 min) | loading or unavailable |
| Magnetic latitude (AACGM) | 51.1° |
Hour by hour, EDT
7 PM
Kp –
– ☁
No
8 PM
Kp –
– ☁
No
9 PM
Kp –
– ☁
No
10 PM
Kp –
– ☁
No
11 PM
Kp –
– ☁
No
12 AM
Kp –
– ☁
No
1 AM
Kp –
– ☁
No
2 AM
Kp –
– ☁
No
3 AM
Kp –
– ☁
No
4 AM
Kp –
– ☁
No
5 AM
Kp –
– ☁
No
6 AM
Kp –
– ☁
No
Rules checked · Built by Radif Partners · How the answer works
- Kp to see it from Erie
- 6.8
- Storm level needed
- G3 (Strong)
- Kp for aurora overhead
- 7.5
- Most clear dark hours
- September
Pennsylvania sees the northern lights only in strong geomagnetic storms. In the AACGM model its towns lie between 48.4 and 51.1 degrees magnetic latitude, around the G3 line that NOAA's storm scale draws at 50 degrees. Erie, on Lake Erie in the northwest corner, needs a planetary Kp of about 6.8; Scranton about 7.0; State College 7.1; Pittsburgh 7.1; and Philadelphia 7.3. Those are all G3 storms, which NOAA counts at about 200 per eleven-year solar cycle. Clouds are the second obstacle: Erie's NASA POWER cloud amount reaches 85% in December, under lake-effect weather. The best ground is the forested north tier, where the Pennsylvania DCNR runs Cherry Springs State Park as a dark sky park. The tool opens on Erie; type your own town or ZIP code.
The north tier and Cherry Springs
Pennsylvania's best asset for the aurora is not its latitude but the emptiness of its northern counties. The Allegheny Plateau along the New York border is mostly forest, with small towns and very little light. Cherry Springs State Park, on a mountaintop in Potter County, is managed by the Department of Conservation and Natural Resources as a dark sky park, and its astronomy field gives an open view of the sky that most of the eastern United States has lost. On a G3 night it is one of the few places within a day's drive of Philadelphia, Pittsburgh and New York where a low red aurora stands out against a truly dark horizon.
The ridge-and-valley country farther south has more relief and more towns; there, hilltops and fire towers with a northern view do better than valley floors. Wherever you stand, the aurora at Pennsylvania's thresholds sits within a few degrees of the northern horizon, so trees and hills to the north matter more than altitude.
What Kp does this town need?
Kp to see aurora from here
7.1
| Magnetic latitude (AACGM) | 49.6° |
| Kp for aurora overhead | 8.2 |
| Storm level | G3 Strong |
| How often that level comes | about 130 days per 11-year cycle |
View line: the more southern of the SWPC oval rule and the NOAA G scale latitudes at each Kp.
Lake Erie and the cloud calendar
Erie has the lowest threshold of the state, Kp 6.8, but also its cloudiest winters. When cold air crosses the warm lake in late autumn and early winter, it builds the lake-effect bands that bury the snowbelt and cover the sky for days, which is why Erie's cloud amount climbs to 85% in December in NASA POWER averages. State College, inland, ranges from 54% in September to 74% in December. Across the state, September is the clearest month and the autumn months lead by clear dark hours.
What a Pennsylvania aurora looks like
Most sightings here are of a diffuse glow low over the northern skyline, pink to red, with sometimes a faint green band at its base and pale rays rising from it. SWPC explains that red light comes from oxygen above about 300 km, which is the part of a distant aurora that clears the horizon from this far south. The eye picks up the color poorly in that faint light; a phone camera on a long exposure records it well, as the phone guide explains. The Pittsburgh page and the Philadelphia page give the figures for the two cities.
Kp needed across Pennsylvania
| Town | Magnetic latitude | Kp to see it | Kp overhead | Storm level |
|---|---|---|---|---|
| Erie | 51.1° | 6.8 | 7.5 | G3 (Strong) |
| Scranton | 49.8° | 7.0 | 8.1 | G3 (Strong) |
| State College | 49.6° | 7.1 | 8.2 | G3 (Strong) |
| Pittsburgh | 49.5° | 7.1 | 8.3 | G3 (Strong) |
| Harrisburg | 48.9° | 7.2 | 8.5 | G3 (Strong) |
| Philadelphia | 48.4° | 7.3 | 8.8 | G3 (Strong) |
Darkness and clouds by month in Erie
| Month | Dark hours | Dark sky, 15th | Mean cloud | Clear dark hours |
|---|---|---|---|---|
| January | 11.2 h | 6:52 PM to 6:06 AM | 84% | 1.8 h |
| February | 10.2 h | 7:26 PM to 5:41 AM | 82% | 1.9 h |
| March | 9.0 h | 9:00 PM to 5:57 AM | 77% | 2.1 h |
| April | 7.2 h | 9:42 PM to 4:57 AM | 76% | 1.7 h |
| May | 5.5 h | 10:31 PM to 4:01 AM | 75% | 1.3 h |
| June | 4.3 h | 11:11 PM to 3:30 AM | 68% | 1.4 h |
| July | 4.9 h | 10:59 PM to 3:53 AM | 61% | 1.9 h |
| August | 6.6 h | 10:07 PM to 4:42 AM | 59% | 2.7 h |
| September | 8.3 h | 9:05 PM to 5:26 AM | 58% | 3.5 h |
| October | 9.8 h | 8:11 PM to 6:00 AM | 70% | 2.9 h |
| November | 11.0 h | 6:35 PM to 5:34 AM | 74% | 2.8 h |
| December | 11.5 h | 6:30 PM to 6:01 AM | 85% | 1.7 h |