  In topological phase transitions involving a change in topological invariants
such as the Chern number and the $\mathbb{Z}_2$ topological invariant, the gap
closes, and the electric polarization becomes undefined at the transition. In
this paper, we show that the jump of polarization across such topological phase
transitions in two dimensions is described in terms of positions and monopole
charges of Weyl points in the intermediate Weyl semimetal phase. We find that
the jump of polarization is described by the Weyl dipole at $\mathbb{Z}_2$
topological phase transitions and at phase transitions without any change in
the value of the Chern number. Meanwhile, when the Chern number changes at the
phase transition, the jump is expressed in terms of the relative positions of
Weyl points measured from a reference point in the reciprocal space.
