Solar Cycle Progression

The observed and predicted ​Solar Cycle is depicted in Sunspot Number in the top graph and F10.7cm Radio Flux in the bottom graph.

The predicted progression for the current solar cycle (Cycle 25) is given by the magenta line, with associated uncertainties shown by the shaded regions. This prediction is based on a nonlinear curve fit to the observed monthly values for the sunspot number and F10.7 Radio Flux and is updated every month as more observations become available. The shaded regions show the uncertainty in the prediction, obtained by applying the same prediction method to previous cycles at the same stage in each cycle. In particular, the three shades show the first three quartiles (25, 50, and 75%) of the deviations from previous predictions.

This should be interpreted as follows. There is roughly a 25% chance that the smoothed sunspot number will fall within the darkest shaded region at a particular time in the future. Similarly, there is a 50% chance the smoothed sunspot number will fall in the medium-shaded region and a 75% chance it will fall in the lightest of the shaded regions.

These plots, like many on the SWPC website, are interactive.

• Mousing your cursor over the plots will display the data values applicable to the date the cursor is over.
• Left clicking on the data and holding while you drag will define a zoom window.
• Use the buttons above each plot to return to the default zoom showing the current cycle or to show the entire available data set.
• There is also an option to toggle the solar cycle numbering on/off.
• Beneath each main plot window, the entire time series is shown and you can click/hold on either side of the blue shaded region to expand or contract the zoom window or if you click/hold on the blue shaded region itself, you can slide it to anywhere in the time series.
• A drop down menu above and to the right of each plot allows you to PRINT, or download PNG, PDF, or SVG format images of the associated plot
• Another drop down menu in the lower left to allows the user to plot the prediction made for Solar Cycle 25 by an international NOAA/NASA/ISES Panel in 2019, as well as the stated uncertainty in this prediction. 

Note that both the updated prediction and the 2019 NOAA/NASA/ISES Panel prediction apply only to Solar Cycle 25. Solar Cycle 26 is expected to begin some time between January 2029 and December 2032.  We do not yet produce a prediction for Solar Cycle 26.  

Solar cycle predictions are used by various agencies and many industry groups. The solar cycle is important for determining the lifetime of satellites in low-Earth orbit, as the drag on the satellites correlates with the solar cycle, especially as represented by F10.7cm. A higher solar maximum decreases satellite life and a lower solar maximum extends satellite life. Also, the prediction gives a rough idea of the frequency of space weather storms of all types, from radio blackouts to geomagnetic storms to radiation storms, so is used by many industries to gauge the expected impact of space weather in the coming years.

The solar cycle prediction shown here is based fitting the observed data to a nonlinear function that reflects the average shape of solar cycles and that takes into account the observed tendency for stronger cycles to rise faster than weaker cycles. Different curves are used to fit the International Sunspot Number and the F10.7 radio flux. Uncertainties are based on applying the same prediction method to previous Solar Cycles, at the same point in each cycle, and then calculating the difference between the predicted and the observed smoothed monthly values. For further technical details, please consult the validation document.

The 2019 Panel prediction comes from an international Panel that was convened in 2019 by NOAA, NASA and the International Space Environmental Services (ISES) for the express purpose of predicting Solar Cycle 25. After an open solicitation, the Panel received nearly 50 distinct forecasts for Solar Cycle 25 from the scientific community. Prediction methods include a variety of physical models, precursor methods, statistical inference, machine learning, and other techniques. The prediction released by the panel is a synthesis of these community contributions. The Prediction Panel predicted Cycle 25 to reach a maximum of 115 occurring in July, 2025. The error bars on this prediction mean the panel expects the cycle maximum could be between 105-125 with the peak occurring between November 2024 and March 2026. The updated prediction can be considered as a re-calibration of the 2019 Panel prediction based on new observational data.

The original version of the Solar Cycle 25 prediction, released in 2019, only showed the baseline NOAA/NASA/ISES Panel prediction. In February 2023, the Sunspot Number and F10.7 radio flux plots were modified to show the full range of the 2019 Panel prediction, taking into account expected uncertainties in the cycle start time and amplitude.

In October 2023 the updated prediction for Solar Cycle 25 was made available to the public as an experimental product on the Space Weather Prediction Testbed.  After a period of feedback from SWPC customers and the general public, the updated prediction was made available on this web site in  February 2025, replacing the 2019 Panel prediction.  However, the Panel prediction can still optionally be displayed using the drop down menus.