Rapid City, SD · magnetic latitude 52.5°
Northern lights in Rapid City: tonight’s chance
Rapid City sits where the Black Hills meet the plains; the northern horizon lies over the plains, not the hills.
Tonight at Rapid City, SD
…
Reading the SWPC Kp forecast and the cloud forecast…
| Kp forecast during the dark hours | not yet forecast |
|---|---|
| Kp needed here | 6.5 (G2 moderate) |
| Cloud cover in the dark hours | loading |
| Dark sky (Sun 18° down) | 7:47 PM to 5:30 AM MDT |
| Moon | 13% lit |
| Right now, OVATION (30 to 90 min) | loading or unavailable |
| Magnetic latitude (AACGM) | 52.5° |
Hour by hour, MDT
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 Rapid City
- 6.5
- Storm level needed
- G2 (Moderate)
- Kp for aurora overhead
- 6.7
- Most clear dark hours
- September
From Rapid City the northern lights need a planetary Kp of about 6.5, a G2 (Moderate) storm on the NOAA scale. The city lies at 52.5 degrees magnetic latitude in the AACGM model, and the aurora reaches overhead only around Kp 6.7. Its position at the eastern foot of the Black Hills shapes the experience: the hills rise to the west and southwest, while the plains to the north and east are open, dry and very dark. Rapid City's NASA POWER cloud amount is lowest in August, at 42%, and highest in February, at 67%, one of the lower winter figures among the cities on this site. By clear dark hours, the best months are September, November and October. The city is in the Mountain time zone, so the tool gives its hours an hour behind Sioux Falls.
Hills to the west, plains to the north
Rapid City grew along Rapid Creek where it leaves the Black Hills, and the city looks two ways. To the west, the pine-covered hills rise above town; to the north and east, the land drops onto the high plains. For the aurora, which at Rapid City's threshold sits low in the north, the plains side is the one that matters. The country along the highways north toward Belle Fourche or northeast toward the Cheyenne River is sparsely settled, with a nearly flat northern skyline and very little light.
Badlands National Park, about an hour east, is a well-known stargazing destination, with dark skies over eroded buttes. Its formations face every direction, so a high overlook with an open northern view is the place to wait for a storm there.
What Kp does this town need?
Kp to see aurora from here
6.5
| Magnetic latitude (AACGM) | 52.5° |
| Kp for aurora overhead | 6.7 |
| Storm level | G2 Moderate |
| How often that level comes | about 360 days per 11-year cycle |
View line: the more southern of the SWPC oval rule and the NOAA G scale latitudes at each Kp.
Dry air and Chinook nights
The western half of South Dakota is semi-arid, and Rapid City's skies are often clear, with less winter cloud than the eastern cities in NASA POWER averages. Warm downslope winds off the Black Hills can bring mild, clear nights in the middle of winter, with gusts. The National Weather Service forecast used by the tool covers the grid cell of the place you choose, so a site on the plains can differ from the city.
Mountain time and the forecast blocks
Rapid City runs on Mountain time, seven hours behind Universal Time in winter. The SWPC block from 03 to 06 UT is therefore 8 to 11 pm locally, and the block from 06 to 09 UT runs from 11 pm to 2 am, the stretch SWPC describes as the most active part of the night. Visitors arriving from the Central time zone sometimes look an hour too early; the hour strip of the tool is written in local time, so following it avoids the mistake.
Compared with its neighbors
Rapid City needs about the same storm as Sioux Falls and Billings, and a little more than Bismarck, 5.3. Driving north into North Dakota or Montana lowers the threshold; driving into the hills raises the darkness but closes the horizon. The South Dakota page lists the other towns, and the Billings page the closest western neighbor.
Kp needed around Rapid City
| Town | Magnetic latitude | Kp to see it | Kp overhead | Storm level |
|---|---|---|---|---|
| Aberdeen | 54.3° | 5.8 | 5.8 | G2 (Moderate) |
| Watertown | 53.9° | 6.0 | 6.0 | G2 (Moderate) |
| Pierre | 53.1° | 6.4 | 6.4 | G2 (Moderate) |
| Sioux Falls | 52.6° | 6.5 | 6.7 | G2 (Moderate) |
| Rapid City | 52.5° | 6.5 | 6.7 | G2 (Moderate) |
Darkness and clouds by month in Rapid City
| Month | Dark hours | Dark sky, 15th | Mean cloud | Clear dark hours |
|---|---|---|---|---|
| January | 11.3 h | 6:22 PM to 5:41 AM | 65% | 3.9 h |
| February | 10.2 h | 6:59 PM to 5:13 AM | 67% | 3.4 h |
| March | 8.9 h | 8:35 PM to 5:26 AM | 66% | 3.0 h |
| April | 7.0 h | 9:22 PM to 4:22 AM | 63% | 2.6 h |
| May | 5.0 h | 10:17 PM to 3:20 AM | 62% | 1.9 h |
| June | 3.7 h | 11:03 PM to 2:43 AM | 52% | 1.8 h |
| July | 4.4 h | 10:48 PM to 3:10 AM | 42% | 2.5 h |
| August | 6.3 h | 9:48 PM to 4:06 AM | 42% | 3.7 h |
| September | 8.2 h | 8:42 PM to 4:54 AM | 44% | 4.6 h |
| October | 9.8 h | 7:45 PM to 5:32 AM | 56% | 4.3 h |
| November | 11.0 h | 6:06 PM to 5:08 AM | 60% | 4.4 h |
| December | 11.6 h | 5:59 PM to 5:36 AM | 65% | 4.1 h |