Where the numbers come from
Every forecast on this site comes from live public data, NOAA's own space weather feeds, an open weather API, and well-documented astronomical formulas. No proprietary black box, nothing we can't point to. Here's exactly what feeds the number on your screen, and how often it updates.
NOAA SWPC, Kp index
The planetary Kp index, the standard measure of geomagnetic activity, straight from NOAA's Space Weather Prediction Center: the 1-minute observed feed plus their 3-day forecast. One detail most forecast sites skip, NOAA publishes Kp two ways, a floored integer that rounds 1.67 down to a flat 1, and the true fractional value. We use the fractional one.
SOLAR-1, real-time solar wind (Bz)
Bz is the north-south tilt of the solar wind's magnetic field, measured about 1.5 million km from Earth at the L1 point, currently by NOAA's SOLAR-1 spacecraft, which took over as the operational L1 monitor after DSCOVR was retired on June 30, 2026. When Bz turns south (negative), Earth's magnetic field opens up and lets solar wind in. It's the earliest and single best real-time signal that a substorm is coming, often 15–60 minutes before it hits. Most consumer Aurora apps don't surface it at all; we do.
Open-Meteo, cloud cover
An Aurora that's happening but hidden behind cloud isn't a sighting. We pull hourly cloud cover for each location's exact coordinates, three days out, and show two numbers side by side: your actual odds tonight, and what they'd be if the sky were clear.
Sun position, twilight & darkness
Aurora needs real darkness, not just an absence of daylight. Sunrise, sunset, and the twilight bands are calculated directly in your browser from your coordinates and the date, using the standard solar-position formula. We treat astronomical twilight (sun 12°–18° below the horizon) and true night (past 18°) as two different states: through the shallower twilight band we only count the Aurora as visible once geomagnetic activity is elevated (Kp 3+, from field observation): the residual sky glow otherwise washes out anything fainter. Past 18°, each location's usual Kp threshold applies with no penalty. This mostly matters for a few weeks each spring and late summer, when high-latitude locations lose and regain true night.
Meeus algorithms, moon phase
Moon phase, illumination, and rise/set times aren't fetched from anywhere. They're calculated directly in your browser using Jean Meeus's simplified astronomical algorithms, the standard reference method for this kind of calculation. A bright moon washes out faint Aurora, so moonlight is factored into the forecast alongside cloud and geomagnetic activity. Accurate to within a minute or two for rise/set, and within a few percentage points for illumination (closest near new/full moon, loosest near quarter moons), more than enough for planning a night outside.
If you want the deeper mechanics, Bz explained and the Kp index go further. And if you want to know who's actually running this, see about.