Space weather refers to the particulate and electromagnetic conditions impinging upon the Earth associated with solar activity outbursts. These result from or are associated with coronal mass ejections, solar or galactic energetic particles, flare effects, geomagnetic storms, etc. There may also be relevance to long term climate change and other areas affected by solar variability. Yet the solar cycle is very difficult to predict. The first figure shows why solar activity prediction is difficult.
Variability is observed at a wide variety of periods.
Aside from curve fitting and climatological, these numerical methods have little justification for their use at all. Nevertheless, new methods may be helping to defeat this age-old problem. These appear to reasonably successful in predicting the Sun's activity on the decadal time scale. Precursors are early signs of the size of the next solar cycle's activity that manifest themselves before the main body of the solar cycle arrives. Much as a darkening sky presages a storm, early signs of a cycle's activity may manifest itself as a harbinger of future solar activity.