Are the Northern Lights only visible when it’s cold outside?

Northern Lights are completely independent of any terrestrial weather conditions, least of all the local temperature. Aurora occurs at high altitudes, 75-400 km or so, way above the troposphere. 

This persistent myth is perhaps understandable though since the aurora is only seen when the sky is dark enough. For Iceland, that means from autumn, through winter into spring, or from late August to late April. On those season, clear skies often go hand in hand with low temperatures. 

Let’s look at the data. First we have average temperature data for Iceland in 2023 from the Icelandic Met Office. As one can see, Iceland is not exactly known for being a warm place to begin with, with December, January and February being the coolest months. That year, March was unusually cold.

Now let’s compare with the annual frequency of the Northern Lights. The graph below shows magnetic disturbance (Northern Lights) caused by the solar wind over a few years. 

As you can see, the Northern Lights are ongoing all throughout the year. The aurora is actually most common in spring and autumn, least common in the winter.  

During the summer months, the nights never get sufficiently dark for aurora to become visible. That’s why we don’t see any Northern Lights in May, June and July. They’re simply lost in the bright summer nights.

Aurora is only visible when the nights are sufficiently dark. In Iceland, the nights are dark enough from early to mid August through September, October, November, December, January, February, March and until end of April. 

So there you have it, backed up by data, Northern Lights and cold weather is a myth.