by Jonathan M. Stern
With Flight Simulator version 5.1, visibility is controllable downward to 1/16 of a mile and specific cloud types are programmable.
Visual flight rules require three miles visibility or greater. When flying on instruments, you will want to ensure that you have at least the minimum visibility required to execute the instrument approach to your destination airport, a figure that is shown in the landing minima section of each approach chart. Low visibilities significantly increases the difficulty of the flights and may hamper learning, because it is tremendously helpful to correlate the out the windsreen view to the instrument indications.