That is true. He could do it. But there is the problem of the Tauntan. If the saber did produce that temperature, they wouldn't need to rest inside of the the warm carcass, therefore, by the movie's logic, the saber doesn't produce much temperature.
Too much wind. Tauntaun was also only temporary as he set up a shelter.
If you had 5000° you could make a hot tub in the snow.