When painting watercolors en plein aire (at an outdoor location), real problems exist for me that aren't present in the studio: the dryness, wind, temperature, etc. Watercolor paints dry very quickly, the watercolor paper dries out too soon, bugs get in my paint, sometimes people even interrupt me to see what I am doing! I enjoy that last part but must keep working to avoid weather conditions.
This watercolor of a small Catholic church in Manitou Springs was painted from the curb on a great morning. I was using Arches 140 lb paper clipped to a piece of masonite and Windsor - Newton watercolor paints in a travel box.