How cold is Uranus during the day? Uranus is the coldest planet of our solar system, with temperatures  as low as minus 224 degrees Celcius. Daytime does not make that  much difference, since Uranus is so f … ar from the sun that it is  hardly more than a big star there.So from a practical point of  view it is basically always night.ranus is the coldest planet of our solar system, with temperatures  as low as minus 224 degrees Celcius.