Install the appClear Aurora on your home screen, in one tap.
Tonight
Reading the solar wind, the Kp index and the local weather.
- Best window—
- Clouds tonight—
- Sky visibility—
- Kp——
- Bz——
- Bt——
- Solar wind——
- Density——
Conditions in —
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Hourly forecast
Next nights
Auroral oval (NOAA)
Why this score?
What to do tonight?
- Loading…
All measurements
| Measurement | Value | Status |
|---|---|---|
| Geomagnetic activity (Kp) | — | — |
| Bz magnetic field | — | — |
| Solar wind | — | — |
| Auroral oval (Ovation) | — | — |
| Darkness | — | — |
| Clouds | — | — |
| Moon | — | — |
| Light pollution | — | — |
Tonight hour by hour
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Loading the forecast…
Hour-by-hour table
| Hour | Darkness | Clouds | Forecast Kp | Moon | Chance |
|---|
Current hour: chance worked out live. Next hours: NOAA Kp forecast (3-hour blocks), forecast darkness and clouds. Bz and solar wind speed cannot be forecast beyond an hour.
Next nights
in —Best time of each night, from forecast solar activity and clouds. Beyond 48 hours, clouds are not forecast yet.
3-day Kp forecast
NOAA SWPCDark bars: observed. Light bars: forecast. Dotted line: approximate Kp needed for your place.
Clouds hour by hourThe sky hour by hour in —
Viewing map
—Clouds on the map only cover France. For your place, they are in “Tonight”.
Best spots near —
- Working it out…
How spots are ranked
Points tested every 5 to 12 km within the chosen radius. Ranking: lowest cloud during full darkness (Open-Meteo grid), multiplied by sky darkness (Lorenz atlas, 18 to 21.5 mag/arcsec²), with a slight preference for nearby points.
Hold the phone flat, top pointing ahead.
Where to look
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Photography
All photo settings
Watching well
- Look north: low on the horizon in France, high in the sky or even overhead in Lapland, Iceland or northern Norway. “Where to look” above gives the detail for your place.
- Escape the lights: a park, a lake or a hill away from street lights already helps a lot, and a 20-minute drive out of town changes everything. The “Map” tab shows the dark spots.
- Bring your phone in night mode, or a camera with a 5–15 second exposure. It sees colours far better than the eye.
- Let your eyes adjust for 15 minutes, without looking at a white screen. Night vision, in Settings, turns the page red.
- Be patient: an aurora comes and goes, often in waves of 10 to 30 minutes.
Auroral ovalWhere are the auroras right now?
—Aurora probability from the NOAA Ovation model for the next 30 to 90 minutes. Hover over the globe to read a value.
Auroras form a ring around the pole. The coloured area shows where they are right now: the closer it gets to you, the better your chances.
Bz and Bt
—nTNorth–south component of the solar wind field, timed to its arrival at Earth. Below zero (green area), the door is open.
Speed and density
—km/sSolar wind measured at the L1 point and propagated to Earth. The hatched area is already on its way.
Estimated Kp over 6 h
—Minute-by-minute estimate from ground magnetometers. The official Kp is published every 3 hours.
Hemispheric power
—GWEnergy deposited by particles in the northern hemisphere (Ovation model). Above 50 GW the oval widens; above 100 GW it can reach France.
How does an aurora form?
- The Sun blows. It constantly sends particles into space. During an eruption, it sends far more, and faster.
- Earth guides them. Its natural magnet steers these particles towards the poles. The stronger the “wind”, the further from the poles they reach.
- The sky lights up. Hitting the air more than 100 km up, they make it glow green, red or purple.
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Recent NOAA alerts
Last 72 hours, geomagnetism.
Source status
Age of the latest data in each feed.
| Source | Latest data | Read at | Status |
|---|
How the score is calculated
The score is an estimate, not a measurement. It multiplies geomagnetic activity by the local viewing conditions.
- Activity: gap between the estimated Kp (max. of the last 20 minutes) and the Kp needed at your geomagnetic latitude (calibrated on France, about
7 + (49 − latitude) / 3). The gap is adjusted by the mean Bz (past 30 min and next hour) and the solar wind speed, then run through a logistic curve. 70% of the result. - Oval: distance between your latitude and the edge of the Ovation oval (probability ≥ 10%). 30% of the result.
- Under the auroral ring (Lapland, northern Norway, Iceland, Alaska…): an aurora shows on most clear nights, even when Kp is low. A base share, zero in France and on the edge of the auroras, rises to 45% for a geomagnetic latitude of about 64 to 71° and is combined with activity: chance = 1 − (1 − activity) × (1 − base). It raises the score and never lowers it. It is an estimate drawn from observers’ common experience, not a measurement.
- Darkness: sun below −12° = 100%, between −6° and −12° = 45%, bright twilight = 10%, daytime = 0.
- Clouds: current Open-Meteo cover; 100% cloud removes 95% of the score.
The Moon and light pollution are shown but are not part of the score: they mostly hinder faint auroras. For a strong aurora, a zone 4 sky is often enough.
Chance levels: none below 10%, low from 10 to 29%, possible from 30 to 54%, good from 55 to 79%, very good from 80%.
Hour by hour and next nights: for the coming hours, activity comes from the NOAA Kp forecast run through the same logistic curve (without Bz or speed adjustments, which cannot be forecast), combined with the local base share, then multiplied by the darkness and clouds forecast for each hour.
Sky visibility: from the clouds forecast tonight (good below 25%, fair below 60%, poor above), lowered one step by a town sky and another by a nearly full Moon that is up.
Best spots: for each point tested, (1 − cloud in the best dark hour) × (0.35 + 0.65 × sky darkness) × (1 − 0.15 × distance / radius). Selected points are at least a quarter of the radius apart.
Height above the horizon: worked out for the red top of an aurora 300 km up, above the edge of the oval, allowing for the curvature of the Earth.
Data sources
- NOAA SWPC: propagated solar wind (satellite at L1), 1-minute estimated Kp, 3-hour Kp, 3-day forecast, G scales, alerts.
- NOAA Ovation: auroral oval forecast 30–90 min ahead.
- Open-Meteo: current and forecast cloud cover (Météo-France, ECMWF models…), on a 580-point grid (one every 55 km or so) covering France, and place search.
- EUMETSAT: live Meteosat infrared image, every 10 to 15 minutes.
- 2025 Light Pollution Atlas by David J. Lorenz, computed from VIIRS satellites.
- NASA GIBS: night images from the NOAA-20 satellite (VIIRS day/night band). The raw version is published a few hours after the pass, the corrected Black Marble version two to three days later.
- Sun and Moon: calculated in the page.
- Base maps: Natural Earth (public domain), via world-atlas.
Automatic refresh: solar wind and Kp every minute, oval and forecasts every 5 minutes, weather every quarter of an hour.