The effect of bedding levels and trailer compartment on internal trailer temperature and relative humidity (RH) during loading and transport of finishing pigs was evaluated in cold and mild weather. Three levels of bedding were used in each experiment: 0.6 m3, 1.2 m3, and 2.4 m3. In mild weather, internal temperatures were lower when 1.2 m3 or 2.4 m3 of bedding were used during loading and transport compared to 0.6 m3 (P < 0.05). Internal trailer temperature increased in a quadratic fashion in the top front compartment when 1.2 m3 was used (P < 0.05), and in a linear fashion in the top rear compartment when 2.4 m3 were used in cold weather (P < 0.05). In mild weather, temperature increased linearly in the top front compartment with heavy bedding levels. Relative humidity increased in a linear fashion in the top front compartment with 0.6 m3, bottom front with 1.2 m3, and top front with 1.2 m3 in cold weather (P < 0.05). In general, temperature and RH increased as bedding levels increased in both cold and mild temperatures. Excess bedding can absorb more moisture, resulting in transport loss and decreased animal welfare.