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Climatic conditions in Canada show extreme seasonal variation, and thermal conditions during transport are known to contribute to mortality during transport. However, little information has been published on transport conditions in Canada. In this study, temperature and relative humidity were monitored on commercial livestock trucks transporting pigs to market in eastern and western Canada. In the western trials, pigs traveled for 8 h in a dual-purpose pot-belly (PB) trailer, and in the eastern trials pigs were transported for 2 h in either a PB trailer or a double-deck (DD) truck. In the west, three trials were done in winter and five in summer; in the east, six trials were done in both summer and winter. Delta temperature (T) and delta humidity ratio (HR) were calculated versus ambient conditions during transport for each truck compartment. Mixed model analyses of compartment conditions (delta T and delta HR) within each truck showed that significant variation existed between compartments in both the PB trailer and the DD truck (p < 0.0001). For all vehicles, delta T and delta HR were generally higher (p < 0.05) in lower-front compartments and lower (p < 0.05) in upper-rear compartments in both summer and winter. The results indicate that transport conditions may be improved by increasing ventilation to targeted compartments in summer, or by a combination of insulation and ventilation in winter. Considering the impact of thermal conditions during transport on pig welfare and mortality, further investigation of truck conditions and ways of ameliorating them is warranted. [ABSTRACT FROM AUTHOR]