Arizona, California, and Nevada are under an extreme heat warning as temperatures are forecasted to hit dangerous levels through Sunday. The National Weather Service (NWS) has issued warnings for areas below 5,000 feet, including eastern Cochise County, the upper Gila, San Pedro, Santa Cruz river valleys, and the Altar Valley in Arizona, where temperatures could reach 100°F (38°C). In south-central and southeast Pinal County, the Tohono O'odham Nation, Tucson, and western Pima County, temperatures may climb to 108°F (42°C). Southern California and southern Nevada are also expected to experience extreme heat, posing significant risks to tourists and those unaccustomed to such conditions.