As a planet orbits the sun, if its rotation axis is tilted, the portion that is tilted toward the sun will receive an excess of sunlight and energy (summer), while the hemisphere which is tilted away from the sun will receive less sunlight and energy (winter). Half a year later, the hemisphere which receives the most sun will be reversed. The fact that there may be an excess or a loss of light and energy affects planetary weather. Because Uranus lies on its side, with the north pole facing the sun, Uranus' seasons should be very strange. The north pole faces the sun, which means it is in daylight, and the atmosphere in that hemisphere never rotates to the dark side to cool. The south pole faces away from the sun, and the atmosphere in that hemisphere never rotates into daylight to warm up. As Uranus orbits the sun, the north pole will be in daylight for half of a year (spring and summer). This means a Uranus day is the same as a Uranus summer. The weather of such a planet should be very strange.
As a body shrinks, it’s angular momentum, the spin rate, increases. All the planets save Uranus generally line up with their poles in the same direction. Uranus spins at a 90 degree tilt. Either it took one large hit to wobble it off it’s axis and settled sideways, or it just might be a captured planet.