The current solar cycle that began in December 2019 is Solar Cycle 25. It is the 25th numbered sunspot cycle since systematic records began in 1755.
Solar cycles track the roughly 11-year rise and fall of sunspot activity. Cycle 25 began at the solar minimum in December 2019, following Solar Cycle 24. Scientists initially expected it to be relatively weak, but its activity became stronger than many forecasts predicted.
The cycle’s peak is determined from smoothed sunspot numbers rather than one unusually active day or month. Solar activity affects space weather, including radio disruptions, satellite operations, radiation conditions, and auroras. The cycle is expected to continue toward a new minimum around 2030.
A common mix-up is confusing the cycle number with its duration. “25” identifies its place in the numbered sequence; it does not mean the cycle lasts 25 years.