The number of X-class solar flares — the most powerful and potentially dangerous class of solar eruption — hit a new record high in 2024. The spike highlights that we are currently experiencing a surprisingly active solar maximum, which could continue to intensify this year.

But solar activity may not be the only reason the number of supercharged solar explosions skyrocketed last year, experts told Live Science. There were a total of 54 X-class flares in 2024, according to SpaceWeatherLive.com, which maintains the oldest and most accurate publicly available dataset on solar flares. That is the highest total since at least 1996, when this dataset began. NASA has been tracking solar flare activity since the mid-1970s, but earlier data has not been made publicly available and is less reliable than modern records, SpaceWeatherLive.com representatives told Live Science in an email. The previous record number of X-class flares in the dataset was 34, recorded in 2001, and only on four other occasions — in 2000, 2003, 2005 and 2014 — has the annual total risen above 20. So last year’s total represents a surprisingly sharp spike in X-class flare frequency.

The effects of the more frequent X-class flares were widely felt on Earth in 2024. For example, in May, a quickfire succession of at least four X-class flares launched clouds of plasma, known as coronal mass ejections (CMEs), that slammed into Earth and sparked the strongest geomagnetic storm in 21 years, which in turn triggered some of the most vibrant and widespread aurora displays in our skies over the last 500 years.

The obvious reason for the increased frequency is the arrival of solar maximum. This peak in the sun’s roughly 11-year cycle of activity, which is triggered by the weakening and eventual flipping of the sun’s magnetic field, has been surprisingly active so far and is expected to continue well into 2025 and possibly beyond.

In October 2024, scientists from NASA and the international Solar Cycle Prediction Panel (SCPP) announced that we have entered solar maximum and that the explosive peak likely started early last year, which was sooner than they had initially predicted. The ongoing maximum has also proved to be more active than most scientists had initially forecast. For example, in August, the number of visible sunspots on our home star, which is a key metric for monitoring solar activity, reached a 23-year high.