400728 19: Sun rays illuminate the desert February 7, 2002 north of Las Vegas, NV where the primary proposed rail route for transporting radioactive waste to the site of Yucca Mountain lies. Although the route would skirt around downtown Las Vegas, many residents dislike the idea of shipping 70,000 tons of nuclear waste over nearby highways and railroads. In January, the U.S. Department of Energy endorsed the Yucca Mountain plan. U.S. President George W. Bush could annouce his support for the plan as early as this week. (Photo by David McNew/Getty Images)

Las Vegas is bracing itself for the first major heat wave of the season. The National Weather Service has issued an excessive heat warning in effect from 11 a.m. Saturday until 9 p.m. Wednesday. There will be a prolonged period of dangerously hot temperatures over Father’s Day weekend, which are expected to hit as high as 115 degrees in southern Nevada. The popular Lake Mead National Recreation Area urged visitors to stay away from outdoor activities during the hottest part of the day, between 11 a.m. and 6 p.m., and also ordered them to stay away from closed trails, saying they may be cited if caught. The National Park Service closes the Goldstrike Canyon and Arizona Hot Spring trails each year between May and September because of excessive heat risks.