Question 1

Why does the app say "Book it" but there are clouds in the forecast?

Accepted Answer

The verdict is Book it when conditions are good enough to make aurora viewing likely — but that doesn't always mean zero clouds. A clear 2-hour window during the dark hours is enough to trigger a green verdict, even if the rest of the night is cloudy. The hour-by-hour chart shows exactly when that window is. It's also possible that a nearby location within a short drive has much clearer skies, which upgrades the verdict.

Question 2

What is Kp and what number do I need?

Accepted Answer

The Kp index is a global scale from 0 to 9 measuring geomagnetic storm strength. The higher the Kp, the further south the aurora extends. The threshold depends on your geomagnetic latitude — not your geographic one. Tromsø (Norway) needs only Kp 1 because it sits directly under the aurora oval. Inverness (Scotland) needs Kp 4+ for a faint sighting and Kp 6+ for a reliable show. The app applies the correct threshold automatically for each city.

Question 3

Why can't I see the aurora in summer?

Accepted Answer

Aurora happens year-round — the Sun doesn't stop being active in summer. But you need a dark sky to see it, and in Arctic regions from roughly May to August the sun barely sets (midnight sun). The sky never gets dark enough, even during strong geomagnetic storms. The best months are September to March, with October–November and February–March often being peak season due to the equinox effect.

Question 4

ECMWF and GFS show different cloud cover — which one is right?

Accepted Answer

Both models can be right — or wrong. ECMWF (European Centre) is generally considered the more accurate global model, especially for cloud cover, which is why it drives the main verdict. GFS (US model) is shown as a second opinion. When they agree, confidence is high. In practice: if ECMWF says clear and GFS says cloudy, lean towards going outside — ECMWF has a better track record for cloud forecasting in high latitudes.

Question 5

How far ahead can I trust the forecast?

Accepted Answer

Cloud cover: reliable up to about 48–72 hours. Beyond that, errors grow significantly — treat Day 3 as an indication, not a guarantee.

Kp / solar activity: the 3-day NOAA forecast is fairly reliable when a known solar event is en route. The most reliable solar data is the live Bz reading, which shows current conditions — but only 30–60 minutes ahead.

Question 6

What does "Drive & Go" mean?

Accepted Answer

It means the selected city is too cloudy locally, but there is a significantly clearer location nearby where aurora viewing may be viable tonight. The app checks the nearest locations using ECMWF cloud data and shows the best option with the drive time. If all nearby spots are also overcast, you'll see a "no escape route" message instead.

Question 7

I went outside on a "Book it" night and saw nothing — why?

Accepted Answer

A few common reasons: (1) Timing — aurora is strongest during substorms, which last 20–60 minutes with quiet gaps. Stay out for at least 90 minutes. (2) Bz turned north — the forecast was good but the solar wind's magnetic field was pointing the wrong way when it arrived, suppressing activity. Check the live Bz. (3) Clouds — local cloud moved in faster than predicted. (4) Light pollution — aurora is faint at low Kp; even modest light pollution can hide it.

Question 8

Does the moon affect aurora viewing?

Accepted Answer

A full moon adds light pollution and makes faint aurora harder to see with the naked eye — but it doesn't block strong aurora. A Kp 5+ display will be clearly visible even under a full moon. For photography, a bright moon can actually be an asset, illuminating the landscape while aurora colours the sky above. Moon phase and rise/set times are shown on each forecast night card.

Question 9

All my nights show "Skip it" — should I give up?

Accepted Answer

If you have flexibility, wait — forecasts beyond 2–3 days can shift significantly, and a cloudy outlook today may clear by the weekend. Check back daily as your trip approaches.

If you're time-constrained, don't write them off entirely. Compare cloud cover percentages and Kp across your nights and pick the least unfavourable one. Lower clouds, a higher Kp, or a short clear window overnight are all reasons to try. Aurora hunting always involves some luck — sometimes you go out on an unlikely night and the clouds part just long enough.

Time	Kp
10:00	2.3
13:00	1.3
16:00	1.7
19:00	2.0
22:00	2.7
01:00	3.0
04:00	2.3
07:00	2.0

Time	Kp
10:00	2.3
13:00	1.3
16:00	1.7
19:00	2.0
22:00	2.7
01:00	3.0
04:00	2.3
07:00	2.0

🏴󠁧󠁢󠁳󠁣󠁴󠁿 Inverness — Aurora Forecast

The Northern Lights