A day after a tiny desert community in Southern California reached 108 degrees, forecasters warned that the record-breaking winter heat across the Southwest will continue into the weekend. North Shore, California, on Wednesday tied a mark first set at Rio Grande City, Texas, in 1954. It's the highest March temperature ever recorded in the U.S. Temperatures will top 100 degrees across Arizona on Thursday. The aptly named town of Thermal, in the desert northeast of San Diego, is forecast to hit 110 degrees on Friday.