Has the sun already passed solar maximum?

We know that the sun has entered its peak phase of activity, called solar maximum. But are we still in it, or is solar maximum already behind us? Let's see what the data has to say.

Although we cannot see it with our bare human eyes, the sun is highly dynamic. On the sun's surface, regions of concentrated magnetic fields manifest themselves as dark sunspots. Above sunspots, active regions in the sun's atmosphere produce solar flares and coronal mass ejections (CMEs), both of which can influence Earth via space weather.

However, the frequency of sunspots, solar flares and coronal mass ejections is not constant. Instead, it rises and falls throughout an 11-year solar cycle. At the bottom of this solar cycle, called solar minimum, months can pass without a single sunspot. At the peak of the cycle — called solar maximum — sunspots, flares and CMEs are commonplace.

We have tracked solar cycles for hundreds of years by counting the number of sunspots on the sun. Since December 2019, at the solar minimum marking the end of Solar Cycle 24, we have been in Solar Cycle 25. Cycles typically last around 11 years, but the exact duration between subsequent solar minimums varies from cycle to cycle.

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At the start of Solar Cycle 25, the National Oceanic and Atmospheric Administration's (NOAA) Space Weather Prediction Center published its official solar cycle prediction, based on an average of predictions from the scientific community. The prediction anticipated that a solar maximum peak of 101.8 to 125.2 monthly sunspots would occur close to July 2025.

However, Solar Cycle 25 has already exceeded the predicted peak, reaching a 13-month smoothed monthly value of 156.7 in August 2024. The 13-month smoothed value of a given month is determined by the average of the specific month, with six months on each side of it (reaching 13 months total). Therefore, there is a six-month lag until this value is available, with August 2024 being the most recent data point as of March 2025.

This smoothed value will likely continue to rise, but it also depends on the sunspot totals in the coming months. It is the peak of this 13-month smoothed curve — not the highest individual month — that determines the peak of the solar cycle.

The graph above displays the solar cycle evolution from 2010 to present. The black line shows monthly sunspot values, and the purple represents the smoothed average. From this graph, we can see that Solar Cycle 25 (from 2019 to present) has already exceeded the size of Solar Cycle 24.

The largest individual sunspot month of the cycle so far, August 2024, had a sunspot total of 216. Since then, monthly totals have been much lower, ranging from 136 to 166 between September 2024 and March 2025. Is this a sign that solar maximum has already passed? Maybe, but maybe not.

The NOAA Space Weather Prediction Center has an experimental solar cycle prediction graph that's currently publicly available in its online testbed. This experimental prediction is a rolling one; it updates each month as the most recent month of data becomes available. Because it is made using up-to-date data, and not a prediction from before any solar cycle data was available, it is far more accurate than the 2019 prediction — and perhaps the most accurate predictor we have for the remainder of the solar cycle.

The most recent version of this prediction, which was updated in March 2025, is presented below. Per this current prediction, solar maximum has most likely already passed, with a peak between August and November 2024. If this is true, then we could already be in the declining phase of Solar Cycle 25.

This solar maximum date is very different from the original prediction of July 2025. So how can this be? Not all solar cycles are exactly 11 years in length. In general, the larger the solar cycle, the shorter it is. Because the amplitude of our current cycle has already far exceeded the predicted peak, it is therefore likely that the true solar maximum date will also precede the original prediction.

So is that it, then? Has solar maximum already come and gone? Perhaps not. Looking back to the first solar cycle graph shown in this article, we see that Solar Cycle 24 had two peaks — one in 2012, and a second in 2014. This double peak rarely features in predictions, but it has been observed many times across historic solar cycles. Could Solar Cycle 25 exhibit a second peak, delaying solar maximum until later in 2025? It is certainly possible, although some may argue that we've already experienced two peaks, in 2023 and 2024, respectively.

These peaks are not as clearly separated as in previous solar cycles, but they do produce a clear inflection in the smoothed solar cycle curve. Ultimately, we will have to wait another year or so to know when the true peak of the solar cycle occurred.

Even if the specific monthly peak of the cycle has passed, it doesn't mean solar activity is over. Strong solar activity persists for a year or two beyond the maximum date, so we still have some time to enjoy sunspots, coronal mass ejections, and any geomagnetic storms and aurora shows associated with them.

Originally posted on Space.com.

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