  In this paper we investigate commuting involution graphs in classical affine
Weyl groups. Let $W$ be a classical Weyl group of rank $n$, with $\tilde W$ its
corresponding affine Weyl group. Our main result is that if $X$ is a conjugacy
class of involutions in $\tilde W$, then the commuting involution graph
$\mathcal{C}(\tilde W, X)$ is either disconnected or has diameter at most
$n+2$. This bound is known to hold for types $\tilde A_n$ and $\tilde C_n$, so
the main work of this paper is to prove the theorem for types $\tilde B_n$ and
$\tilde D_n$.
