While a predictive, microscopic theory of nuclear fission has been elusive, advances in our understanding of nuclear structure are allowing us to make significant progress. Through nuclear energy density functional theory with an interaction fit only to ground state and isomeric observables, we calculate the fission barrier heights and spontaneous fission half-lives of several actinide nuclei. We find good agreement between our calculations and known experimental data, lending confidence to the predictions of our theory beyond experimentally measured nuclei. We also study the effects of temperature on the mass yields and hyperdeformed isomers of thorium-232 and uranium-232. While microscopic theories tend to underestimate the depth of the hyperdeformed isomer in these nuclei, we find that the isomers can be revealed by heating the systems to modest excitation energies.