"There's so little sunlight that far from the sun that Jupiter's upper atmosphere should be frigid, scientists estimate it should be about -100 degrees Fahrenheit (-73 degrees Celsius), according to a NASA statement. However, the average temperature in Jupiter's upper atmosphere is a roasting 800 degrees F (426 C) — almost as hot as the surface of the hellish planet Venus."
An interesting problem to solve at Jupiter. There should be no lingering heat or primordial heat remaining at Jupiter from its origin some 4.5 billion years ago using the meteorite dating paradigm. Other Jovian exoplanets do show higher temperatures too in some examples.
The Extrasolar Planet Encyclopaedia — Kepler-87 b (exoplanet.eu)