The average temperature of Jupiter is believed to be minus 145 C. However, the planet's temperature varies widely, and it is one of the hottest places in the solar system at its center.
Most of Jupiter is made of gas, so an item dropped on it would fall to its core. As the pressure imparted on the falling object increases, its temperature increases as well. At its core, Jupiter is believed to be approximately 35,000 C, and the pressure is enough to make the hydrogen it contains into liquid. Jupiter's core is second only to the Sun in terms of heat.