Transition jitter is one of the most important parameters for evaluating the potential areal density of Heat Assisted Magnetic Recording. However, obtaining this either experimentally or through micro-magnetic simulation is time consuming. Here, we show that the more easily calculated thermal switching probability distribution (SPD) can serve as a substitute. In particular, we provide an equation relating the standard deviation of write temperature to the jitter. The equation is verified for three critical noise sources: Tc variance, HK variance, and grain size distribution. In addition, the SPD subject to cooling at various cross-track positions is investigated. A method to determine the magnetic grain size is proposed.