As semiconductor technology continues to evolve, the chip temperature increases rapidly due to the exponentially growing power consumption. In the meantime, the high chip temperature increases the leakage power, which is becoming the dominate part in the overall power consumption for sub-micron IC circuits. A power/thermal-aware computing technique becomes ineffective if this temperature/leakage relation is not properly addressed in the sub-micron domain. In this paper, we study the feasibility problem for scheduling a hard real-time periodic task set under the peak temperature constraint, with the interaction between temperature and leakage being taken into consideration. Three analysis techniques are developed to guarantee the schedulability of periodic real-time task sets under the maximal temperature constraint. Our experiments, based on technical parameters from a processor using the 65 nm technology, show that the feasibility analysis without considering the interactions between temperature and leakage can be significantly overoptimistic.