Based upon empiric evidence of a cargoes transport using sea freight container, a record captured that the Temperature inside container could reach beyond 64.3deg C corresponding with its Relative Humidity inside container at 21.4%.
Above mentioned circumstances occurs in a 40 feet container / 67.7 cbm, which in simple words we can say that those container holds more than 2.25 kg water molecule; awaiting to condense and damaging the cargoes (and most likely its packaging). For some other parts of the world it is highly possible that they could be even worst.
Temperature modifiers during transport most likely affected by day and night cycle and the weather. Only refrigerated container can hold off the effects and maintain it at preferred level. Unfortunately refrigerated container rent is very expensive and few available. Most of general commodities exporters use the standard / hard-top container; which unmanageable for the temperature.
Relative humidity initially determined by the fresh air on the loading location, with a high possibility for changes because of following factors:
a. evaporated / absorbed water molecule from goods / cargoes
b. evaporated / absorbed water molecule from the packaging materials
c. evaporated / absorbed water molecule from container floor made of wood (which may after washed out)
d. evaporated / absorbed water molecule from outside the container, from its ventilation, rusted holes, or even a shabby rubber container door seal.
Relative humidity flows from higher to lower; it means carrying water molecule to lower RH. Above the sea or in a container yard, this can be adding water molecule inside container.