This paper presents an assessment of fire weather and fire behavior predictions produced by a numerical weather prediction model similar to those used by operational weather forecasters when preparing their forecasts. The PSU/NCAR MM5 model is used to simulate the weather conditions associated with three fire episodes in June 2005. Extreme fire behavior was reported across the Southwest, Great Basin, and Southern California Incident Areas during this time period. By comparing the simulation results against reports of extreme fire behavior, the ability of the model to differentiate between the three episodes is assessed, and relationships between weather conditions and extreme fire behavior are suggested. The results of these comparisons reveal that the most extreme fire behavior occurred in locations where near-ground temperatures were the highest. While relative humidity did not vary substantially across the three episodes, variations in temperature led to a greater potential for evaporation and fuel drying, which could have been a factor in the observed extreme fire behavior. Additional analyses reveal that the diurnal variations in mixed layer processes also explain some of the variability in fire behavior in the episodes.