Tool
Northern Lights in Maine: Tonight’s Forecast
Most nights the honest answer is no. This shows the current number, what it would take, and where in Maine it would be visible if it happened.
Right now
Planetary K index is 0.00.
Below the threshold for aurora anywhere in Maine. Quiet conditions; nothing to go outside for.
The forecast against the dark
A storm only counts if it happens while the sky is black where you are standing. Here is the three-hourly forecast with the properly dark hours shaded behind it: what matters is whether a bar clears one of the dotted lines inside a shaded block.
Three-hourly planetary K index from NOAA, faded where the value has already been observed rather than forecast. The shaded blocks are true darkness at Caribou — the sun eighteen degrees down — so a bar outside one is a storm nobody in Maine can see. Tonight it is dark from 9:32 PM to 3:38 AM, with a predicted peak of Kp 4.00 in that window: Unsettled.
- Dark at Caribou from 9:35 PM to 3:36 AM, highest planetary K index in that window 4.00.
- Dark at Caribou from 9:32 PM to 3:38 AM, highest planetary K index in that window 4.00.
- Dark at Caribou from 9:30 PM to 3:40 AM, highest planetary K index in that window 4.00.
- Dark at Caribou from 9:28 PM to 3:42 AM, highest planetary K index in that window 3.00.
Next three days
| Day | Peak Kp | What that reaches |
|---|---|---|
| Wednesday, Aug 19 | 4.00 | Unsettled |
| Thursday, Aug 20 | 4.00 | Unsettled |
| Friday, Aug 21 | 3.00 | Below aurora threshold |
Peak of NOAA’s three-hourly predicted values for each day, in Eastern time. A peak at noon is no use to anyone; check the timing before planning a night out.
What each level reaches
| Kp | Level | Where in Maine |
|---|---|---|
| 4+ | Unsettled | A faint glow low on the northern horizon from the far north of Aroostook County, on a dark, clear night, with a camera more likely to catch it than the eye. |
| 5+ | G1 minor storm | Visible along the northern horizon from Aroostook County and the North Woods. Rarely anything to the naked eye further south. |
| 6+ | G2 moderate storm | Reaches the middle of the state: Moosehead, Baxter, the Downeast coast and inland Hancock County. |
| 7+ | G3 strong storm | Most of Maine, including the midcoast and, away from town lights, the Portland area. |
| 8+ | G4 severe storm | The whole state, overhead in the north, and bright enough to be obvious rather than something you have to look for. |
When it is dark enough
The other half of the problem, and the half nobody checks. Northern Maine has barely two hours of true darkness around the June solstice, so a once-a-decade storm in midsummer would still be a washout. Autumn through early spring is when the sky can hold up its end.
Astronomical night on the fifteenth of each month at Caribou, in Eastern time: the hours when the sun is more than eighteen degrees below the horizon and the sky is genuinely black. This month is outlined. The moon is a separate problem — the week either side of a full moon costs you most of this whatever the clock says.
Where to stand
You want darkness and an open northern horizon. These have both, and almost nothing lit north of them.
- Aroostook County, around Caribou and Presque Isle: The furthest north you can drive to easily in Maine, and the first part of the state the oval reaches. Potato fields give you a horizon most of the state cannot.
- Moosehead Lake at Greenville: Forty miles of dark water pointing north-west, with the nearest real light pollution a long way south.
- Baxter State Park and Millinocket: One of the darkest skies in the eastern United States. Togue Pond gives an open northern view without a summit hike.
- Rangeley Lakes: High, dry and dark, with lake surfaces to open the horizon. Better odds than anywhere else in western Maine.
- Quoddy Head and the Bow Tie coast: Far east, very dark, and the Bay of Fundy sits to the north-east. Clear nights are less common here than inland, which is the trade-off.
- Schoodic Peninsula: The most accessible dark northern horizon on the Acadia side, and far quieter than Mount Desert Island after dark.
Common questions
Can you see the northern lights in Maine?
Yes, but not often and not everywhere. Northern Maine sits far enough north that a moderate geomagnetic storm puts a glow on the horizon a few times a year. Southern Maine needs a strong storm, the kind that makes the news. The far north of Aroostook County has by far the best odds.
What Kp number do I need?
Roughly Kp 5 for a low glow from Aroostook County, Kp 6 to reach the middle of the state, and Kp 7 before the midcoast and the Portland area are realistic. Those are rules of thumb: the auroral oval is not a neat circle and a substorm can brighten one sector for twenty minutes and then fade.
When is the best time of night?
Around local midnight, give or take a couple of hours, when your part of the earth is pointed most directly at the tail of the magnetosphere. You also need real darkness, so the weeks either side of a full moon are much worse, and June is close to hopeless because it never gets properly dark.
Where should I stand?
Somewhere with an open view north, away from town lights, with water or open ground in that direction rather than hills. The coast east of Schoodic and the North Woods both work well because there is very little light north of you.
What can the Kp number not tell me?
Whether your own sky is clear, whether the moon is up, and whether the substorm arrives while you are still awake. Kp is a planetary average over three hours, and a Kp 6 under cloud is worth exactly as much as a Kp 1. It is backward looking by design too: the current reading describes the last few minutes, and the forecast predicts a planetary index rather than your horizon. Treat a promising number as a reason to check the sky, not as a promise.
