We examined the role that season progression and social threats play in the heat‐aggression hypothesis within Major League Baseball put forward by Reifman, Larrick, and Fein (). Box score data from 38,870 Major League Baseball games between the years of 2000 and 2015 was used to test the heat‐aggression relationship, while accounting for temporal and social factors that may be simultaneously exerting influence on player behavior. Controlling for a number of other variables, we observed that the effect of temperature on aggressive behavior is partially contingent on the point of the season in which the game took place. Aggressive behavior was also more likely to occur when teams played divisional (compared to league and inter‐league) rivals, however this relationship was contingent on season progression. We provide potential boundary conditions relating to the heat‐aggression relationship, indicating this may not be a ubiquitous phenomenon.