With increasing temperatures, Schwinger pair production changes from a
quantum tunnelling to a classical, thermal process, determined by a worldline
sphaleron. We show this and calculate the corresponding rate of pair production
for both spinor and scalar quantum electrodynamics, including the semiclassical
prefactor. For electron-positron pair production from a thermal bath of photons
and in the presence of an electric field, the rate we derive is faster than
both perturbative photon fusion and the zero temperature Schwinger process. We
work to all-orders in the coupling and hence our results are also relevant to
the pair production of (strongly coupled) magnetic monopoles in heavy ion
collisions.