The atmosphere is vital to a planet’s evolution. In this talk, I will explore how atmospheres affect heat flow in giant planets both within and beyond the Solar System. Using Juno mission data and numerical simulations, I will reveal a stable layer inside Jupiter that points to a warmer interior and resolves discrepancies in Juno’s gravity data. This layer divides Jupiter’s weather into separate convective zones, restricting heat and chemical transport. Similar dynamics on Saturn and ice giants limit cloud formation and vertical mixing. I will also share new insights into the cooling of “hot Jupiters” and their inflated sizes, reshaping our understanding of these enigmatic worlds.