Gas turbines operating in extreme temperatures demand safety, efficiency, long service lives, and reduced in-service inspection frequency. This paper examines and extends the available models for representing the effects of temperature on the design-critical fatigue crack growth rate (FCGR) behavior of materials used in hot-section turbine disks and blades. The FCGR data gathered from the literature are used to evaluate and extend previously proposed models, and the phenomenological bases for the models are explored. The FCGR rate trends in disk alloy ME-3 across five temperatures and two load ratios are included in the data analyzed. Similarly, FCG data on a blade alloy, directionally solidified (DS) GTD-111, in two orientations are used to evaluate the model. The model constants are derived and listed in the paper. The improved model is shown to capture the FCGR trend in both materials. Thermally-activated dislocation mobility mechanisms are associated with the effects of temperature on the FCGR behavior. These mechanisms include dislocation nucleation, cross-slip of screw dislocations, climb of edge dislocations, and dislocation recovery, each exhibiting a characteristic activation energy. Factors that lead to transient FCG behavior are also explored, and recommendations are made for future studies.