  We consider the well-known phonon scattering induced high-temperature
linear-in-$T$ metallic resistivity, showing that a naive extrapolation of the
effective linearity from high temperatures to $T=0$ leads to an apparent
zero-temperature negative resistivity. The precise magnitude of this
extrapolated $T=0$ negative resistivity depends on the temperature regime from
where the extrapolation is carried out, and approaches the correct physical
result of zero resistivity at $T=0$ only if the extrapolation starts from $T\gg
T_D$, where $T_D$ is the Debye temperature. We establish a theoretical
relationship between the negative intercept and the slope of the linear-in-$T$
resistivity as a function of the temperature $T$ from where the extrapolation
is carried out. Experimental implications of our finding are discussed for the
much-discussed Planckian behavior of the transport scattering rate.
