The Effect of Ambient Temperature on the Movement of a Baseball Pitch

Abstract

While prior studies acknowledge environmental effects on the movement of a baseball pitch, most rely on
observational in-game data with uncontrolled variables, leaving a gap in experimental research that isolates the role of
ambient temperature. To address this, we investigated the effect of ambient temperature on the vertical and horizontal
movement of fastballs, curveballs, and sliders across three controlled conditions: cold (55°F), average (70°F), and hot
(85°F). We hypothesized that pitch movement across all three pitch types would decrease as ambient temperature
increased due to reduced air density and aerodynamic forces. Pitches were delivered using a calibrated three-wheel
pitching machine at 54.2 feet and recorded using video-tracking software. Relevant external variables were controlled
to isolate the impact of temperature. Results demonstrate an inverse relationship between temperature and pitch
movement, with colder conditions producing increased movement. Curveballs and sliders exhibited the greatest
sensitivity to temperature changes, with increases in vertical and horizontal movement in colder air, while fastballs
showed more subtle variations. To support these findings under controlled conditions, a Python-based simulation was
constructed using drag models, isolating temperature-dependent air densities and horizontal/vertical wind vectors.
The computational model further demonstrated that the reduced velocity decay and trajectory deflection observed in
warmer air are driven by density-induced reductions in drag force, establishing a theoretical baseline that bridges
physical field data with fluid dynamic principles. These findings highlight the role of environmental conditions on
pitch behavior, offering insights for players and coaches to account for weather conditions when evaluating pitch
movement.