The climate of Titan, the largest moon of Saturn, is similar in many respects to that of Earth, despite having a far lower surface temperature. Its thick atmosphere, methane rain, and possible cryovolcanism create an analogue, though with different materials, to the climatic changes undergone by Earth during its far shorter year.
Temperature
Titan receives just about 1% of the amount of sunlight Earth does. The average surface temperature is about 90.6 K (-182.55 °C, or -296.59 °F). At this temperature water ice has an extremely low vapor pressure, so the atmosphere is nearly free of water vapor. However the methane in the atmosphere causes a substantial greenhouse effect which keeps the surface of Titan at a much higher temperature than what would otherwise be the thermal equilibrium.
Haze in Titan's atmosphere contributes to an anti-greenhouse effect by reflecting sunlight back into space, making its surface significantly colder than its upper atmosphere. This partially compensates for the greenhouse warming, and keeps the surface somewhat cooler than would otherwise be expected from the greenhouse effect alone. According to McKay et al., "the anti-greenhouse effect on Titan reduces the surface temperature by 9 K whereas the greenhouse effect increases it by 21 K. The net effect is that the surface temperature (94 K) is 12 K warmer than the effective temperature 82 K. [i.e., the equilibrium that would be reached in the absence of any atmosphere]"
Seasons
Titan's orbital tilt with respect to the Sun is very close to Saturn's axial tilt (about 27°), and its axial tilt with respect to its orbit is zero. This means that the direction of incoming sunlight is driven almost entirely by Titan's day-night cycle and Saturn's year cycle. The day cycle on Titan lasts 15.9 Earth days, which is how long it takes Titan to orbit Saturn. Titan is tidally locked, so the same part of Titan always faces Saturn, and there is no separate "month" cycle.
Seasonal change is driven by Saturn's year: it takes Saturn about 29.5 Earth years to orbit the Sun, exposing different amounts of sunlight to Titan's northern and southern hemispheres during different parts of the Saturnian year. Seasonal weather changes include larger hydrocarbon lakes in the northern hemisphere during the winter, decreased haze around the equinoxes due to changing atmospheric circulation, and associated ice clouds in the South Polar regions. The last equinox occurred on August 11, 2009; this was the spring equinox for the northern hemisphere, meaning the southern hemisphere is getting less sunlight and moving into winter.
Surface winds are normally low (<1 meter per second). Recent computer simulations indicate that the huge dunes of soot like material raining down from the atmosphere in the equatorial regions may instead be shaped by rare storm winds that happen only every fifteen years when Titan is in equinox. The storms produce strong downdrafts, flowing eastward at up to 10 meters per second when they reach the surface. In late 2010, the equivalent of early Spring in Titan's northern hemisphere, a series of methane storms were observed in Titan's equatorial desert regions.
Due to the eccentricity of Saturn's orbit, Titan is about 12% closer to the Sun during the southern hemisphere summer, making southern summers shorter but hotter than northern summers. This asymmetry may contribute to topological differences between the hemispheres - the northern hemisphere has many more hydrocarbon lakes. Titan's lakes are largely placid, with few waves or ripples; however, Cassini has found evidence of increasing turbulence during the northern hemisphere summer, suggesting that surface winds may strengthen during certain times of the Titanian year. Waves and ripples have also been seen by Cassini.
Methane rain and lakes
The findings of the Huygens probe indicate that Titan's atmosphere periodically rains liquid methane and other organic compounds onto the moon's surface. In October 2007, observers noted an increase in apparent opacity in the clouds above the equatorial Xanadu region, suggestive of "methane drizzle", though this was not direct evidence for rain. However, subsequent images of lakes in Titan's southern hemisphere taken over one year show that they are enlarged and filled by seasonal hydrocarbon rainfall. It is possible that areas of Titan's surface may be coated in a layer of tholins, but this has not been confirmed. The presence of rain indicates that Titan may be the only Solar System body besides Earth upon which rainbows could form. However, given the extreme opacity of the atmosphere to visible light, the vast majority of any rainbows would be visible only in the infrared.