A fast coronal mass ejection (CME) that left the Sun yesterday is expected to reach Earth overnight tonight or on Tuesday morning, bringing the potential for the northern lights to be visible across parts of the UK.

While opportunities to witness the aurora are not uncommon during this active phase of the solar cycle, whether it will be visible hinges on two critical factors: the timing of the CME’s arrival and the local weather conditions on Tuesday evening.

In this blog, we explore what to expect from the incoming solar activity, how weather conditions might affect visibility, and what you need to know if you’re hoping to catch a glimpse of the northern lights.

What is driving the aurora potential?

The CME currently heading towards Earth is a major burst of charged particles ejected from the Sun’s atmosphere. These particles travel through space and, upon reaching Earth, can disturb the planet’s magnetic field. When the disturbance is strong enough, a geomagnetic storm develops, increasing the chances of aurora activity.

During geomagnetic storms, energy from the incoming solar particles interacts with gases high in Earth’s atmosphere. Oxygen and nitrogen emit light at different wavelengths, creating the colourful displays typically associated with the northern lights, from soft greens to vivid reds and purples.

CMEs of this size are relatively common during the current stage of the solar cycle, which naturally brings periods of heightened solar activity. As a result, opportunities for aurora sightings can occur several times a year, especially during the darker months.

Where in the UK could the northern lights be seen?

If conditions align, the aurora could be visible across Scotland, Northern Ireland, and northern England in the early hours of Tuesday. If geomagnetic activity is slightly stronger, the display may extend further south, though this is more difficult to predict. Areas away from city lights, with clear views to the northern horizon, typically offer the best chance of seeing the aurora when it occurs.

However, aurora visibility is always dependent on the CME arriving during hours of darkness. A daylight arrival, even during a strong geomagnetic storm, would prevent the lights from being seen from the UK. Similarly, clear skies are essential; any significant cloud cover can completely obscure the view.

How weather conditions may affect visibility

While the space weather conditions may support aurora activity, the terrestrial weather looks much less favourable for most parts of the UK.

A largely cloudy picture will continue through the night, with further bands of rain pushing northwards, some of which may turn locally heavy, particularly in western areas. Occasional clearer spells may develop in between, however, for aurora viewing, these conditions present challenges.

Krista Hammond, Met Office Space Weather Manager, explains: “There is still some uncertainty around the exact timing of the CME’s arrival, but it is expected overnight tonight or tomorrow morning. The CME is likely to result in geomagnetic storming, giving the potential to view the aurora. However, sightings are dependent on the CME arriving during hours of darkness and clear skies. Unfortunately, cloud and rain on Tuesday evening may make viewing difficult, even if the timing is favourable.

“The effects of the CME may linger into Tuesday night, with aurora sightings possible across Scotland, perhaps also Northern Ireland and northern England, where skies are clear. This is likely to wane further by Wednesday night, perhaps with some glimpses possible from the far north of Scotland.”

READ MORE: What are the Northern Lights and what causes them?

Understanding the northern lights

The northern lights, or aurora borealis, are among the most captivating natural phenomena visible from Earth. Displays can range from faint glows on the horizon to sweeping curtains of vibrant colour that move across the sky. Their variability stems from the complex interactions between solar particles and Earth's atmosphere.

When charged particles from the Sun collide with atmospheric gases, they transfer energy that is then released as light. Oxygen at different altitudes produces green and, more rarely, red light, while nitrogen gives rise to blue and purple hues. The intensity and spread of the aurora depend on the strength of the geomagnetic storm; during very strong events, the lights can be seen much further south than usual.

The UK’s best opportunities to see the northern lights typically occur around the equinoxes, during March/April and September/October, when geomagnetic activity and longer nights often coincide. However, significant solar events can create visibility opportunities at other times of year.

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