  We study the arithmetic of seminormal $v$-noetherian weakly Krull monoids
with nontrivial conductor which have finite class group and prime divisors in
all classes. These monoids include seminormal orders in holomorphy rings in
global fields. The crucial property of seminormality allows us to give precise
arithmetical results analogous to the well-known results for Krull monoids
having finite class group and prime divisors in each class. This allows us to
show, for example, that unions of sets of lengths are intervals and to provide
a characterization of half-factoriality.
