Las Vegas, known for its searing summertime heat and glitzy casino fountains, is projected to get even hotter in the coming years as climate change intensifies. As temperatures rise, possibly as much as 10 degrees by end of the century, according to some models, water demand for the desert community is expected to spike. That is not good news in a fast-growing region that depends largely on a limited supply of water from an already drought-stressed Colorado River.