Jet engines essentially have 3 limits - (1) An internal pressure limit, (2) A turbine temperature (typically EGT) limit, and (3) An engine speed limit. The maximum thrust which may be used at Takeoff (and MCL and MCT in some circumstances) will be when the first of the 3 limits are reached.
Consider an aircraft at Sea Level on a very cold day. As the thrust levers are advanced, the maximum internal pressure would typically be first reached as the air is very cold and dense. The engine is well below the EGT and N1 limit. As ambient temperature increases, the air is less dense, and increasing EGT and N1 is required to achieve the pressure limit, although still below their limits. This is a situation where the engine is "Flat Rated", a rise or fall in ambient temperature will have negligible effect upon thrust, it is "Flat", with the thrust available being quite constant and governed by the internal pressure limit.
Ultimately, with EGT and N1 increasing to achieve the required thrust, the EGT limit will be reached, and as temperature rises further, Fuel Flow and thrust must be decreased. The engine is now in a declining thrust situation with thrust being governed by the EGT limit. This is known as "Full Rating".
Engine speed limiting Takeoff thrust is rare, it is usually a high altitude phenomenom. With decreasing density with increasing altitude, engine speed must be advanced to achieve the required thruct, MCL, MCT etc. When the engine speed is at a maximum, the engine thrust is governed by the engine speed limit.
Fairly typical, but by no means absolute, temperature limit to flat rated thrust is around 30°C. Below that temperature the engine is Flat Rated, above that temperature, it is Full Rated. If you happen to be operating the engine right at the ambient temperature limit for the flat rating, stress is at it's maximum, as the engine is simultaneously at it's pressure and temperature limit.
Regards,
Old Smokey