Skip to content
Search
POLARISWIRE DATA

Solar Cycle 25 tracker

The international sunspot number averaged 60.3 in September 2026, with a mean F10.7 solar radio flux of 105.4 solar flux units. The highest monthly value so far in Solar Cycle 25 is 216.0, recorded in August 2024.

Updated 27 October 2026. Source: NOAA Space Weather Prediction Center; WDC-SILSO, Royal Observatory of Belgium.

Sunspot number, September 202660.3Monthly mean international sunspot number
F10.7 radio flux, September 2026105.4 sfu10.7 cm solar radio emission
Cycle 25 monthly high so far216.0August 2024
12-month average sunspot number91.5A year earlier: 135.4
Monthly international sunspot number, 2008 to date-9501081662252008201120142017202020232026Data: WDC-SILSO / NOAA SWPC · Chart: PolarisWire, polariswire.com/data/solar-cycle-tracker
Line chart of the monthly international sunspot number since 2008. Source: NOAA Space Weather Prediction Center; WDC-SILSO, Royal Observatory of Belgium.

Monthly sunspot number and F10.7 flux, last 24 months

MonthSunspot numberF10.7 flux (sfu)12-month average sunspot number
September 202660.3105.491.5
August 202676.0116.297.3
July 202678.1136.0102.1
June 202693.3138.2106.1
May 2026101.8125.7107.9
April 202679.0120.0105.9
March 202686.6130.7111.1
February 202677.4135.9115.1
January 2026115.0151.2121.6
December 2025124.2160.1123.5
November 202591.7141.6126.0
October 2025114.8139.7131.2
September 2025129.7153.9135.4
August 2025133.7156.1136.4
July 2025125.9137.7143.2
June 2025114.6131.4149.2
May 202578.5135.2153.3
April 2025141.4162.2161.1
March 2025134.2163.8160.7
February 2025155.7184.3158.2
January 2025137.0189.4155.4
December 2024154.6196.9154.5
November 2024154.1199.9151.1
October 2024165.8222.6147.2

About the data

Sunspot numbers are the monthly mean international sunspot number maintained by the World Data Center SILSO at the Royal Observatory of Belgium, as compiled by the NOAA Space Weather Prediction Center. The F10.7 index is the Sun’s radio emission at a wavelength of 10.7 centimetres, measured in Canada by the National Research Council, and is widely used as a proxy for solar activity.

Solar Cycle 25 began in December 2019, the solar minimum identified by the NOAA–NASA Solar Cycle Prediction Panel. Solar activity rises and falls over a cycle of roughly 11 years; higher sunspot counts generally mean more solar flares and coronal mass ejections that can affect satellites, radio communications and power grids.

Monthly values swing widely, so the 12-month average, calculated by PolarisWire from the official monthly figures, gives a steadier view of the trend. Recent values can be revised by SILSO. This page reflects NOAA’s latest published file and is refreshed daily; the chart starts in January 2008, near the start of Solar Cycle 24.

Suggested source citation: Sunspot data: WDC-SILSO, Royal Observatory of Belgium, Brussels, via NOAA Space Weather Prediction Center (swpc.noaa.gov).

Download and reuse

The full series is free to download as CSV. You may reuse this compilation and chart under a CC BY 4.0 licence with credit to PolarisWire and the original source, linking to this page.

Embed this chart

Copy this code to publish the always-current chart on your own site. Please keep the credit link.