Know the sky. Chase the light.
Heliocast answers the moment you open it - a plain-language verdict for exactly where you are, built from live NOAA, NASA and ESA space weather. Then it shows you the working: a 3D aurora map, the solar wind, and alerts that only wake you when the sky is actually clear.
Eight live data feeds. Free to use, no account, no ads.
Features
From a one-glance "can I see the northern lights tonight?" verdict to the same solar telemetry professional forecasters watch - without needing a degree to interpret it.
A plain-language answer the moment you open the app, with the reason behind it. A 0-100 visibility score weighs the NOAA aurora forecast against darkness, moon phase and cloud cover for your exact spot - and daylight or overcast can veto it outright.
The current planetary Kp index straight from NOAA SWPC, backed by the 3-hourly planetary Kp and 1-minute solar-wind telemetry from the L1 point, refreshed continuously.
Spin a real-time globe carrying the OVATION auroral oval and the day/night terminator, so you can see where the aurora is and where it is dark enough to watch it. Six Arctic observatories and all-sky cameras are one tap away.
Every night ahead ranked on darkness, moonlight, cloud and the NOAA aurora forecast, plus an hour-by-hour grid for the next three nights. Free ranks tonight and the next two; Pro ranks the full fourteen.
The SDO solar disk in eight wavelengths plus white-light continuum and magnetogram, SOHO/LASCO coronagraphs, L1 solar wind and the full IMF, GOES X-ray and proton flux, and a CME tracker with arrival times.
Our server watches NOAA's 1-minute feed all night and wakes your phone the moment your threshold is crossed, with the app closed. Cloud-aware and dark-aware, so a storm you cannot see never rings. One overnight Kp alert is free. Pro adds Bz, wind speed, your own visibility score and quiet hours.
App screens
Five tabs, each answering one question. Every screen turns space-weather telemetry into something you can act on in seconds.
Tonight
Open Heliocast and the first thing you get is a human sentence, not a wall of numbers. The score combines the aurora forecast, darkness, the moon and your local cloud - and when the answer is no, it tells you which one of those is the reason.
Nights
The question a trip actually turns on. Heliocast ranks the nights ahead for wherever you point it - your location, or the place you are flying to - and breaks the next three into three-hour blocks so you know when to be outside, not just which day.
Sun & solar wind
Professional-grade solar imagery and telemetry, presented so it is readable. Watch the active regions that produce flares, the coronagraphs that catch a CME leaving the Sun, and the solar wind arriving at L1 an hour before it reaches us.
Activity
Flares, storms and coronal mass ejections, with the part that matters kept in front: when the Earth-directed ones arrive and how big they are expected to be. This is where a good aurora night is visible three days before it happens.
Alerts & journal
Set the conditions that matter to you and let Heliocast do the watching. The two toggles that make the difference are on by default: hold the alert when it is cloudy, and hold it when the sun is up. When a display happens, log it - the conditions save themselves, so you learn what works.
Data sources
Heliocast aggregates the same public feeds professional space-weather forecasters rely on. Everything is fetched and cached on our server, so the app stays fast and the agencies never see anything about you.
Who it's for
Know when and where to set up. Visibility scores, dark-sky windows and alerts that reach you in time to drive out.
Track X-ray flux, proton events and the Bz component to anticipate radio blackouts and propagation changes as they unfold.
Plan a northern lights trip around the best nights available, and learn the science behind every number in the built-in glossary.
Pricing
Heliocast is free forever, with no account and no ads. Pro is a single yearly plan - no monthly tier, no trial countdown, and less than most aurora apps charge for a month. The free tier is the trial.
Free
$0
Forever. No account, no ads
Heliocast Pro
$4.99
Per year. Auto-renews, cancel anytime
About 42 cents a month.
Heliocast Pro is a yearly auto-renewing subscription billed through the App Store or Google Play. It renews at the price shown unless cancelled at least 24 hours before the period ends; manage or cancel it any time in your store account settings. Prices are shown in your local currency in the app. Terms of Use · Privacy Policy
Questions
The things people ask before they download an aurora app - and the science behind the numbers Heliocast shows you.
That depends on four things at once, which is exactly why Heliocast exists. You need geomagnetic activity strong enough to push the auroral oval over your latitude, a sky dark enough to see it against, a moon that is not washing it out, and no cloud in the way. A high Kp on a cloudy evening in June is worth nothing. Heliocast checks all four for your coordinates and gives you a single answer, plus the reason when the answer is no.
Kp is a 0-9 scale of global geomagnetic disturbance, published by NOAA every three hours. Roughly: the higher the Kp, the further from the poles the aurora is visible. At Kp 0 the auroral oval sits near 66.5° magnetic latitude; by Kp 9 it has pushed down to about 48°. It is the single most quoted aurora number, but on its own it never tells you whether you will see anything, because it says nothing about darkness, the moon or your weather.
Bz is the north-south component of the interplanetary magnetic field carried by the solar wind, measured in nanotesla at the L1 point about a million miles upstream. When Bz turns strongly negative - southward - it links up with Earth's own field and pours energy into the magnetosphere, which is what actually lights the aurora. A sustained negative Bz can produce a better display than a higher Kp with Bz pointing north, and because L1 sits upstream you get roughly 30 to 60 minutes of warning.
No. Heliocast works anywhere on Earth, in both hemispheres - the same model handles the aurora australis in Tasmania, New Zealand and southern Chile. During a strong geomagnetic storm the oval reaches well into the mid-latitudes, and the alerts exist precisely so you find out on the nights it does.
Yes. Our server watches NOAA's 1-minute feed all night and sends a push the moment your threshold is crossed, whether or not Heliocast is running. One overnight alert is free. It is cloud-aware and dark-aware by default, so it will not wake you for a storm you could not have seen anyway.
Anywhere far enough north or south, the limit is darkness rather than the aurora itself. High-latitude summer has no astronomical night at all - the sun never drops the 18° below the horizon that a faint aurora needs - so the practical season runs from roughly late August to mid-April in the north, and the mirror months in the south. Heliocast will tell you plainly when there is simply no night to look at.
No account, no ads and no tracking SDKs. Your location is used to compute your forecast and is not sold or shared; the sightings journal, including photos, stays on your device. All the agency feeds are fetched by our server, so NOAA and NASA never see anything about you. The full detail is in the Privacy Policy.
$4.99 per year - one plan, no monthly option and no free trial, because the free tier already is the trial. Pro adds the full 14-night ranking, up to 10 saved places, unlimited precision alerts on Bz, wind speed and your own visibility score, quiet hours, and the weather-radar layer. It renews yearly and you can cancel any time from your App Store or Google Play account.
Yes, both - it is a native app on iOS and Android, and the forecast, the 3D map and the alerts are identical on each.
Free to download. No account required.
