Summer has come to an abrupt end in the Rockies. Cold air from Canada caused temperatures to drop by up to 60 degrees in less than 24 hours Tuesday in Colorado, a day after people fled their homes because of a wildfire that ballooned in hot, windy weather.  Highways in Wyoming including portions of Interstate 80 began closing as snow picked up across the state, where forecasters predicted up to a foot of snow in the mountains. Strong winds have knocked out power in northern Utah. Scattered winter storm warnings and weather advisories are posted from southern Montana to southern Colorado.