Northern lights Portland tonight
Portland sits at 53° magnetic latitude on the Maine coast. Kp 4-5 is the threshold here. Cape Elizabeth gives a north-facing Atlantic horizon 6 miles from downtown, and Acadia National Park 3 hours north offers a Dark Sky-designated summit at 466 meters above the coastal cloud layer. Best season: September to April.
Aurora visibility - Portland
Unlikely tonight
Kp 1 is well below the Kp 4–5 threshold needed for aurora to be visible from Portland.
Current Kp
1
of 9
7-day outlook for Portland
Today
15 May
Tomorrow
16 May
Sun
17 May
Mon
18 May
Tue
19 May
Wed
20 May
Thu
21 May
Based on CME arrival predictions from NASA DONKI. Arrival times ±6 hours.
What Kp is needed here?
Portland sits at a magnetic latitude of approximately 53°N. The Kp index - a global measure of geomagnetic activity on a scale from 0 (quiet) to 9 (extreme storm), updated every 3 hours - needs to reach Kp 4–5 before the auroral oval expands far enough south to be visible from here.
At Kp 4–5, visibility is possible from Portland but skies need to be clear and dark. Cloud cover and light pollution remain the main obstacles even when Kp is high enough.
Best dark sky sites near Portland
Light pollution is the biggest obstacle after cloud cover. These sites give you the best dark northern horizon within reach.
Cape Elizabeth - Fort Williams Park
Rocky Atlantic coastline 6 miles south of Portland. Fort Williams Park surrounds Portland Head Light and opens onto a north-facing shore with the ocean horizon extending to the northeast. Light pollution from Portland is behind you when facing north, and the lighthouse makes a strong foreground for photography. Open year-round and free.
Two Lights State Park
Cape Elizabeth, adjacent to Fort Williams Park. The rocky headland faces north and northeast over the open Atlantic with minimal development nearby. Parking is available at the trail access points, and the exposed shoreline drops most of the ambient glow from Portland. Bortle 4-5 conditions on the coast itself, improving to Bortle 3-4 on the ocean-facing rocks away from the parking area.
Acadia National Park - Cadillac Mountain
Three hours north on Mount Desert Island. At 466 meters, Cadillac Mountain is the highest point on the US East Coast north of Rio de Janeiro, and the summit is accessible by car via the Summit Road from May through November. Acadia carries an International Dark Sky designation, and the summit's 360-degree horizon above the tree line makes it one of the most capable aurora-viewing positions in the northeast. On nights when Portland is marginal, Cadillac is often unambiguously clear.
Best time to see the northern lights in Portland
Portland's aurora season runs from late September through to March, when nights are long enough for truly dark skies. The equinox months, September and March, bring a natural boost in geomagnetic activity, making them statistically the best of the season. Summer months bring too much twilight for aurora to be visible at this latitude.
Activity peaks around the September and March equinoxes, when Earth's magnetic field geometry is most favourable for coupling with the solar wind. Events during these two windows tend to produce the strongest displays of the year for observers at Portland's latitude.
April through August brings persistent astronomical twilight that washes out aurora completely. Even strong events (Kp 6+) remain invisible during this period because the sky never gets dark enough.
Related pages
Northern Lights USA
USA-wide aurora forecast hub.
Northern Lights Burlington Tonight
Burlington - Lake Champlain north-facing horizon at 53° magnetic latitude.
Northern Lights Maine
Maine statewide aurora forecast, from Portland to Acadia and the north woods.
Northern Lights New Hampshire
New Hampshire aurora forecast and White Mountains dark sky guide.
What Is the Kp Index?
What Kp 4-5 means for aurora viewing at 53° magnetic latitude.
Common questions
Aurora watching from Portland and the Maine coast.
