Leslie Young's model for Pluto's year-round climate produced three different kinds of behavior. Top row: with lots of nitrogen and larger thermal inertia, a north polar cap persists all year round. Middle and bottom row: with less volatiles and lower thermal inertia, caps migrate from north to south and air pressure reaches maxima at southern summer solstice and also between perihelion equinox and northern summer solstice. Two caps persist for most of the year when there's a larger volatile inventory. With less nitrogen available, the northern polar cap vanishes quickly after perihelion.