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How to Read the Aurora Forecast

Northern lights

Do you want to see the northern lights in Iceland? There are two good online northern lights forecasts that can help you with finding them. One can be found when visiting the website of the Icelandic Meteorological Office and the other when you go to the website Aurora Forecast. Aurora Forecast uses information they gather from the Met Office but adds more data to it to create a complete overview. Both forecasts can be a little hard to decipher if you have never seen something like this before. In this article, we would like to make things a little clearer.

Northern lights Iceland

Cloud cover is the most important factor

Even though there are several factors at play when it comes to northern lights forecasts, the most important one is cloud cover. Northern lights are formed between 90-150km in the sky but can extend up way higher. Clouds are formed way lower in the sky and can, therefore, easily get in the way. In Iceland, low clouds are clouds located up to 2km, middle clouds between 2-4km, and high clouds between 3-8km in altitude. Cloud cover is difficult to predict, and it’s best to look at cloud cover forecasts as late as possible. Looking at a cloud forecast 24 hours ahead will probably not give you reliable information. Check cloud cover a couple hours before you head out, though, as unfortunately, there’s no chance you will see the northern lights when it’s very cloudy.

Northern lights

How do cloud cover forecasts work?

Both websites show a cloud cover forecast but use different colours to represent cloud layers. The Met Office uses white for no clouds and dark green for very cloudy. The different shades of green mean cloudier or less cloudy. Aurora Forecast uses blue to purple for low clouds, orange to red for mid-level clouds and green for high clouds.

Northern lights

What is kp index?

The kp index, shown on both websites, tells you how likely it is for the lights to be active and how active they will be. It’s a scale of 1 to 9. Don’t be discouraged if the number is low, it’s actually very rare for the number to be higher than 5. Also, take the scale with a grain of salt; a low number doesn’t mean that they won’t come out or won’t be impressive, and a high number isn’t a guarantee that they will be glorious all through the night.

Northern lights

Solar wind and magnetic fields

Aurora Forecast also shows graphs of solar wind speed and the interplanetary magnetic field. Solar wind speed matters, because the faster solar wind is moving, the more energetic it is. And when solar wind is more energetic, aurora storms become stronger. The interplanetary magnetic field is the Sun’s magnetic field carried into space by solar wind. The interplanetary magnetic field connects with the Earth’s magnetic field when they are oriented opposite to each other. When the interplanetary magnetic field is oriented southward, the strongest connection occurs and the strongest aurora are visible. In short, when the solar wind speed is high and when there is a negative south value, aurora will be strong.

Many thanks to Sævar from Aurora Forecast for above explanations!

Northern lights

Going on a tour?

There are many tours taking you far from the bright city lights for a better chance of seeing the aurora. These tours will be cancelled if there is no chance of seeing northern lights. Book your northern lights tour here!

Do you want to know how to photograph the aurora? Then read our guide on how to photograph the northern lights.