I think stuff comes from a warehouse that isn't freezing cold inside (no one would work in that sort of thing), and is loaded into trucks that get a certain amount of residual heat from the friction of the tires on the road below them. There's the truck's exhaust system right below the chemicals too, which is very hot. The truck's cab catches all the freezing wind, but the driver has that big diesel I.C.E. and a good heater to keep them warm.
Plus the stuff is all boxed up, which has an insulation factor. People have been doing this on trains and trucks for how long? If it were an issue, it would have happened over a 100 years ago.