Transient transport in high-temperature and turbulent plasmas is investigated. Microscopic fluctuations in toroidal plasmas are localized in the outside of the torus, so that the radial correlation length of fluctuations is meso-scale (hybrid between micro-scale and system size). The long radial correlation induces the interference of gradient and flux in different radii, and causes a fast propagation of transient response. The upper bound of thermal diffusivity, deduced from transients, is derived. The role of geometry in transport far from thermodynamical equilibrium is highlighted.