Security primitives such as Physical Unclonable Functions (PUFs) or True Random Number Generators (TRNGs), have emerged as hardware roots of trust for ensuring the security of modern applications.  
However, these primitives display susceptibility to physical attacks, among them, in the face of temperature variations. Previous research has established the feasibility of attacks exploiting temperature fluctuations to compromise the security of these primitives. Specifically, when implemented on FPGAs, programmable components can be vulnerable to alterations induced by thermal changes. These findings underscore the need to deepen the understanding of the implications of temperature sensitivity on the security and robustness of these security mechanisms. This paper studies how heat affects, both instantaneously and permanently, the working of ring oscillators, which are the building blocks of PUFs based on Ring Oscillators. The study also suggests how to exploit these effects to bias the PUf responses, enabling thus the possibility of its cloning.