Googling it, although there obviously is an effect on the GPS system when solar activity is high, there seems very little agreement on what the problem actually is. I suspect simple interference with the signal strength is the most likely problem, because the GPS transmissions are incredibly weak anyway (something like 50 Watts from a minimum of 12600 miles away, and received using a non-directional aerial so vulnerable to noise). Other possibilities seem to include altered speed of transmission through the ionosphere, and solar wind interfering with the satellites directly. If these latter last any great length of time then some self-correction takes place within the system. Plus there are currently far more than the specified 24 satellites in active service, offering some redundancy.
In any case GPS is a whole magnitude more accurate than a road cyclist really needs (and if you're riding over Yad Moss, several magnitudes really, there's little scope to go wrong) so a temporarily reduced performance shouldn't pose a problem for cyclists. Drones, another matter.