As a land surveyor that utilizes GPS on a daily basis, I can tell you that weather is typically not going to be much of a hindrance to your GPS reception. There would have to be pretty severe electrical storm activity to disrupt your signal to a point where you lose satellite availability.
Solar activity can be a culprit. Flares can have a very significant impact on gps signal - In my line of work, it usually equates to poor positional accuracy. Still, the satellites should be visible to the Vision.
As suggested by others, your physical position is usually the problem when you cannot see many satellites. Don't assume that just because you are in your open yard or a large field that you will be in good satellite reception areas. If you are in an area lying in a tight valley or with close proximity to high mountains, you may have certain times of the day where satellites are simply not available due to obstructions well beyond your immediate location.
Here's a cool tool from Trimble Navigation for predicting satellite trajectories in your area.
http://www.trimble.com/gnssplanningonline/#/Settings
You can set an elevation mask to limit satellite availability due to long range obstacles in your area such as mountains or buildings.
Just remember that you are tracking
GPS satellites...to my knowledge our receivers can't track glonass, galileo, bei dou, QZSS.
Good luck!
