We investigate the effect of temperature on alpha-particle clustering in the diluted nucleus 16O using the multi-constrained finite-temperature relativistic Hartree-Bogoliubov model with the DD-ME2 interaction. At a critical density, the nucleus undergoes a Mott-like transition from a homogeneous to a localized configuration characterized by alpha-particle clustering and the emergence of a finite nonaxial octupole deformation. We study the interplay between the onset of localization under nuclear dilution and the suppression of deformation and alpha-particle clustering due to increasing temperature. Investigating the temperature-density plane, our findings indicate that temperature delays the formation of nonaxial octupole deformation and alpha-particle clustering in dilute environments. Following the transition from homogeneous to clustered configurations, the nonaxial octupole deformation continues to increase with further dilution of the system and becomes nearly independent of temperature. We found that alpha-particle clusters appear at temperatures up to T = 4.10 MeV and at a corresponding normalized density rho Mott/rho 0 approximate to 0.09.