I present the results of numerical simulation of the seasonal migration of nitrogen frost on Triton constrained by Voyager observations of atmospheric pressure, temperature, and albedo distribution. Most of the exposed nitrogen is probably seasonal frost, whose migration can produce major variations in atmospheric pressure. For instance, models explored here predict a tenfold pressure drop in the coming decade. The observed patterns can be understood if fresh nitrogen frost is relatively dark but brightens with increasing insolation in a manner analogous to the Martian southern CO2 cap.