Paul,

Unpaved Flea Market grounds can be muddy or, if devoid of vegetation, dusty.

The Englishtown, NJ, Flea Market is largely unpaved.  There's little ground
cover; too much traffic.  Locals refer to it as "The Dirt Mall." I can attest
that a hot August day there can be very trying! The dust is blowing around
nonstop!

In heavy rains, these same  grounds flood from a nearby brook.  If you arrive
soon after a long rain, you'll understand.

John Ruth