Northern Lights Tonight is a local go / maybe / no for tonight. It is not a percentage, not a map tracker, and not affiliated with NOAA.
The gates, in order
For each 30-minute slot that is dark enough (sun at or below −12°):
- If aurora data is missing, we do not guess (UNKNOWN).
- If the oval does not reach you, that slot is NO.
- If clouds are socked in, NO.
- Horizon-only plus city glow, or a bright moon on a horizon oval, cannot be GO.
- Only a clear-enough sky with real reach can be GO. Otherwise MAYBE.
Slots that are still twilight are skipped (not dark yet) and do not vote. If the whole night never gets dark enough, the night is NO (summer high latitude).
We do not average a weighted score. We do not print 73%.
Near window vs the rest of the night
The next ~90 minutes use NOAA SWPC OVATION grids (at the point and north along the horizon). Later tonight uses the 3-hour Kp forecast plus, on pages that have a dossier, that place’s typical Kp bands. Mid-latitude and sub-oval pages cannot GO on that far window. A /view pin with no dossier cannot GO on the far window either.
State pages use one headline point
A state is not the max of its cities. Colorado’s headline is the Fort Collins area, not Denver. Oregon’s headline is Baker City, not Portland. Other points can be listed; they do not get their own indexed URL.
Sources
- NOAA Space Weather Prediction Center public products (OVATION and Kp).
- Open-Meteo cloud cover (low / mid / high).
- Local sun and moon from the coordinates in the place dossier.
The browser never calls NOAA. Pages read snapshot files. Stale snapshots display UNKNOWN, not last hour’s GO.
Related: Tonight · How to see