  We investigate how temperature affects transport through large networks of
nonlinear conductances with distributed thresholds. In monolayers of
weakly-coupled gold nanocrystals, quenched charge disorder produces a range of
local thresholds for the onset of electron tunneling. Our measurements
delineate two regimes separated by a cross-over temperature $T^*$. Up to $T^*$
the nonlinear zero-temperature shape of the current-voltage curves survives,
but with a threshold voltage for conduction that decreases linearly with
temperature. Above $T^*$ the threshold vanishes and the low-bias conductance
increases rapidly with temperature. We develop a model that accounts for these
findings and predicts $T^*$.
