Say around 32 C or 90 F, inside, not in the sun, near an open door. Is there a risk a dryer will overheat? Or does it regulate temperature so it'll just not heat as much use less energy to run (with hot days being no more risky than cold ones)?
No, there shouldn't be a problem.
I'm an appliance service technician.
All of the electric dryers that I've seen use a form of electronic thermostat to keep the drum temperature below its operation temperature limit. Often they use two or three at different locations. One of them may require a manual reset, assuring that the user knows that it tripped, to warn of blocked vent for example.
This being the case, there should be no additional danger because of high outside temperature. If the temperature would by some freak be over the design temperature of the machine, it just wouldn't turn on.
Because of several (admittedly well-placed) comments, I am adding a picture of a typical dryer thermostat. Usually they are normal closed, opening at their specified limit somewhere between 65 and 180° C (150-360°F). For reference, the limit for long-term (more than half a day) human survival is supposed to be at approximately a 35°C (95°F) wet-bulb temperature.