Temperature average 59 K (-214 degree C) at the cloud tops, dropping to 55 K at the tropopause before rising to 275 K in the stratosphere due to internal heating; the core reaches ~7,000 K. Strong internal heat (twice the solar input) from gravitational contraction (Kelvin-Helmholtz mechanism), where infalling material converts potential energy to thermal energy, warms the interior to ~7,000 K at the core, powering convection and preventing further cooling. This explains why Neptune radiates more heat than expected, unlike cooler Uranus. The thermosphere anomalously reaches 750 K, possibly from magnetic field-ion interactions, auroras, gravity waves, or dayglow dissociation of  – unrelated to sunlight. Polar troposphere can be 10 K warmer (south pole in 2007), allowing methane sublimation into the stratosphere, while recent southern summer cooling by 10 K defies expectations due to convection “burps” or seasonal dynamics.

Internal heat (more than solar input) drives convection, fueling violent storms, banded patterns, and seasonal changes from its 28 degrees tilt, despite faint sunlight. The hazy, methane-laden atmosphere scatters light for a deep blue hue and lacks solid surface, so “conditions” mean crushing pressures and extreme cold at observable levels, with no stable ground.