If you look at Jupiter in visible light, you will see that it is covered in clouds arranged in bands. The cloud bands that you see on Jupiter block the infrared radiation from leaving the planet. Holes in the clouds let heat through from the deeper and hotter parts of Jupiter's atmosphere.
Click on the picture. This picture shows Jupiter in infrared light and next to Jupiter two people whose pictures were also taken in infrared light. The parts of the people not covered by clothes are sending off a lot more infrared light than those parts covered by clothes. The clothes on the people and the clouds on Jupiter both block the infrared radiation.