Did a little search and pulled this off the FedEx website.
http://images.fedex.com/us/packaging/guides/Perishables_fxcom.pdf
The FedEx Express
Transportation Environment
Perishable products must withstand various temperature
conditions in the FedEx Express shipping environment.
The cargo areas of our vans and trucks are not
temperature-controlled, and temperature will vary
depending on time of year, location, exposure to
sunlight and other variables. In summer months the
temperature in the cargo area of ground vehicles can
be as much as 30 degrees Fahrenheit higher than the
ambient temperature outside the vehicle.
On board FedEx Express aircraft, temperatures vary
depending on the type of aircraft, the location of each
cargo compartment and the package location within
each compartment, the length of flight, and the cruising
altitude. For general reference, temperatures aboard
most wide-body aircraft main cargo compartments vary
between 65 F (18 C) and 90 F (32 C). Packages positioned
in the bulk department, next to the aircraft’s outer
structure, might be exposed to temperatures as low as
0 F (-18 C) during flight.
Air pressures on FedEx Express aircraft vary from as
low as 8.3 psi at cruise altitude to as much as 14.7 psi
on the ground.
