The Solar Cycle Like Earth, the Sun has seasons. It has a cycle that lasts about 11 years. This cycle is marked by an increase and decrease in the number of Sunspots, and has been measured reliably for the last 300 years. The period during which the number of Sunspots is at its greatest is known as Solar Maximum. As you might expect, the period during which the number of Sunspots is lowest is called Solar Minimum. An increase in the number of Sunspots signals an increase in the Sun's magnetic activity. As magnetic activity increases, so does the frequency and intensity of solar storms. Of course, damaging CME’s and Solar Flares can occur at any time. (When do you think the next Solar Maximum should occur?)