The effective temperature of Uranus is -216°C or -357°F. At 1 bar of pressure in the planet the temperature is -197°C or -322.6°F and at .1 bar of pressure in the planet the temperature is -220°C or -364°F. Although Uranus is not the furthest planet from the Sun it is definitely the coldest planet in our solar system. It also has the least warm core at 4,727°C or 8,540.6°F than any of the other gas planets (Jupiter, Saturn, Neptune). Some scientists propose it could be because Uranus may have gotten it’s 97.8° tilt by some massive collision by another large object, then this collision may have caused the core to release a lot of heat.
Another possible reason why Uranus is so cold is because half the planet is always in darkness because of its tilt, and then this lack of sunlight on 50% of the planet causes these extreme cold temperatures, unlike the other gas giants who generally get sunlight on the entire planet within 1 Earth day. Half of Uranus’s planet does not get sunlight for about 42 years. Think about it this way, if you put a ball in the Sunlight for 10 minutes straight, then the part of the ball that was in the shade for 10 minutes straight will obviously be cooler. So if I take the average temperature of the entire ball’s surface (cool and warm areas) it would be lower than the ball’s surface if I continuously rotated it in the Sunlight for 10 minutes (making sure the whole surface gets Sun).