By Steve Gorman LOS ANGELES (Reuters) - Wildfire warnings were posted across parts of three Western U.S. states on Sunday as a heat wave baked the region in record, triple-digit temperatures, stoking flames in California from the coastal foothills outside Santa Barbara to desert brush near the Mexican border. Excessive heat advisories and "red flag warnings" for extreme fire conditions were in effect across southern portions of California, Nevada and Arizona, the National Weather Service reported on the eve of the first official day of summer. In the Los Angeles suburb of Burbank, the mercury topped out at 109 degrees Fahrenheit (42.8 Celsius), shattering the prior record high for the date of 104 degrees set in 1973.
