Fairly typical, but by no means absolute, temperature limit to flat rated thrust is around 30°C.
In the 146, it's only flat rated to a measly 15°C.
At 15°C at MSL, full thrust is 93.5%, any hotter or colder and the full thrust N1 decreases, for the reasons well put by Old Smokey. For example, at 0°C, full thrust is 91.3% and at 30°C it's 91.4%.