How easy is it to catch a glimpse of the spectacular show that is the Aurora Borealis, or Northern Lights, in Sweden?

It depends on where you live. If you’re based in northern Sweden, you probably only have to be patient and you’ll get there eventually. The further north you get, the better your chances, as the Northern Lights only appear around the Earth’s magnetic poles.

But that doesn’t mean the Northern Lights are a safe bet on any given day in northern Sweden; it all depends on solar activity and cloud cover. If the sky is overcast as we mentioned, you’re likely to be disappointed.

In Stockholm and further south, the Northern Lights are relatively rare, but not unheard of.

• KEY TIPS: How to take the best pictures of the Northern Lights in Sweden

There are a few ways you can stay up to date with potential sightings, although the Northern Lights are complex, so they are hard to predict.

Keep an eye on websites such as the University of Alaska’s Aurora Forecast, which for obvious reasons doesn’t focus on Sweden but can still give you a good idea. The Space Weather Prediction Center and SpaceWeather Live are another two reliable websites.

To interpret these, you need to learn a little bit about the Northern Lights. That doesn’t mean you have to become an expert (and our article is aimed at beginners), but it’s useful to know that the key metric to keep an eye out for is something called the “KP Index”, a scale from 0-9.

The KP Index measures geomagnetic activity in the atmosphere; the higher the number, the stronger the geomagnetic activity. You can based on this divide the northern parts of the Earth into zones, where Kiruna in the far north is in KP3 and Stockholm is in KP6. So if, say, a KP3 number is predicted, only northern Sweden is likely to see the Northern Lights.

If you’d rather not have to think too much about when and where to see the Northern Lights – “I just want someone to tell me when they’re on!” – we recommend the Facebook group Norrsken Sverige, which regularly posts daily forecasts during peak season, which tell you exactly when and where the Northern Lights are expected. Followers also post their reports and pictures of the lights as they happen.

You can also download an app. My Aurora Forecast is popular and there are free versions for both iPhone and Android. You can either choose what location you want to track, or tell it to automatically change its settings based on where you are. The app will send you notifications when there’s a high chance of seeing the Northern Lights, but it also gives you a long-term forecast of the KP index. It also gives you percentages for how likely you are to see the Northern Lights in your area, now and in the next 30 minutes.

To make sure the sky is clear, check the weather report on Swedish meteorological institute SMHI’s website.