Helium reionization is an important epoch in the Universe’s history, and the most recent large-scale transition of the intergalactic medium (IGM). Reionization is driven largely by quasars, and has important implications on the thermal history of the IGM. Due to the biased nature of sources and the large degree of photoheating, numerical simulations are ideally suited to investigating this problem. Recently we have run a new suite of large-scale cosmological simulations that solve N-body, hydrodynamics, and radiative transfer simultaneously in order to study the impact of helium reionization on the IGM. Specifically, we make predictions for the temperature density relation of the IGM and observables related to the Lyman-alpha forest. We show that aspects of reionization such as the timing and duration are visible in the helium II Lyman-alpha forest, and might be detectable in the hydrogen forest as well. Most importantly, the gas temperature at mean density is a smoking-gun signal of the timing of reionization.