Generally dogbones and extension cords are pretty safe and a std 30amp cord with a 15a to 30a dogbone will marginally carry the load from an AC.
That said, if ANY plug/socket combination does not fit snuggly together, almost to the point of needing a little lubrication to fit together, you stand a chance of the connection heating up.
Pay attention to your equipment, plug blades and grounds should be clean and bright and the socket's contacts should also be clean, bright and fit the blades tightly.
It is not unusual for the pedestals to have sockets that are loose and burned from plugging in cords with a load on them. Make sure the breaker or switch in the pedestal is OFF before plugging in your cord.
If the pedestal socket is very loose you stand the chance of something overheating.