One of the biggest draws to Iceland is the Northern Lights. During the winter months when it’s dark you can witness this stunning natural phenomenon where green lights flicker and dance through the cold night sky. Typically the lights are visible in Iceland between August and early April.

Here we’ll explain what the northern lights are and how that affects how you look for them, as well as how to use some helpful websites and recommended phone apps.

What are the northern lights and how do they work?

It helps to understand what the lights are before you start hunting for them. The mistake most people make is that they head out to see the lights and are met with a thick wall of cloud, a full moon, or there’s no forecast for the lights in the area that evening. 

The dancing lights, northern lights or the Aurora Borealis (in the northern hemisphere, Aurora Australis in the south) are collisions between electrically charged particles from the sun and Earth’s atmosphere. The particles are drawn to the magnetic north and south poles, which is why you only see the northern lights at high latitudes like in Iceland. 

We often talk about there being a ‘sun storm’ that leads to us seeing the lights. Just like with the rain, if there’s no rain, there are no rainbows. Without these particles coming from the sun carried towards us on a solar wind, there are no northern lights. This is why a forecast will show activity on one day, and not on another. 

What is the KPI index?

When we talk about “activity” or the KPI index, what we’re referring to is how close the particles from the sun are in relation to us on a scale of 0 to 9. The Kp–index describes how much turbulence the solar wind has caused as it interacts with our atmosphere. The faster the solar wind blows, the greater the turbulence and the brighter and more intense the northern lights. 

The scale indicates how intense the geomagnetic storm is likely to be. It will regularly be between 1-3 daily in Iceland, but when it starts to hit 3-6, you’d better grab your camera and a sweater – but no need for a raincoat, it’s not that kind of storm. 

The most common colour we see is green, which is made by particles with oxygen interacting with the atmosphere about 60 miles or 100km above the earth.  Nitrogen rather than oxygen produces blue or purplish-red aurora, which is generally considered a very good Aurora here in Iceland. This is more about the gas in the particles than how dark the sky is, or how “high” it is on the KP index. However, the more particles and the stronger the wind, the higher chance of seeing the lights and the more intense they’re likely to be. 

How to check the forecast

There are a few sites that we recommend for checking activity. By using these you should be able to get an accurate forecast for each night you are here, and for different areas in Iceland. 

Check the cloud cover

Use the Icelandic site vedur.is (which you can select in English) and here you can see an hourly cloud cover forecast to get an idea of the coverage in the area you will be staying. The trick to vedur.is is to remember that the cloud cover is green, and the clear skies are white – it can be a little confusing at first glance!

You can select the language (English or Icelandic) in the top middle of the browser, marked with the flag. If you search “Aurora” in the search bar, or click on any of the coloured images of Iceland it will navigate to a page where the Aurora Forecast becomes available on the browser on the left. If you click that, you’ll see this view with green and white.

On the right hand side it shows you the forecast level on a scale from 1-9, and will give you the sunrise, sunset and moonrise times for the day so you can try to plan your hunting hour-by-hour. You can move the blue button at the bottom hour-by-hour to watch the cloud forecast and the aurora forecast change. 

Check the activity

You can do a basic check of the activity near you using the Vedur.is website and mobile version. We also recommend  the app Aurora – My Aurora Forecast – Aurora Alerts and Northern Lights forecast app for Android or iPhone. The app can be set up to give you a push notification when the KP index is heading above 3, which is when you’ll start seeing green aurora with the naked eye. The in-app cloud coverage prediction isn’t always accurate however, so we would suggest combining the KP and activity predictions from the app with a more up-to-date and local cloud coverage prediction from Vedur.is.

If you’re looking for something more in-depth, Spaceweather.com is a great resource for plain language information about solar activity and storms. They feature a daily forecast on the left hand side, a visual representation of the aurora around the northern and southern hemispheres, and also have an SMS update system you can subscribe to for about USD $4.95 a month that will send you more-in-depth text messages than the Aurora app.