Dangerously hot temperatures across the US south-west will continue to climb this week, reaching higher than 120F (49C) in some areas, exacerbating the region’s already-dire drought conditions and increasing the risk of new fire ignitions. Extreme heat will be felt across much of Utah, along with southern and central California, Nevada and Arizona. More than 48 million people across the west are now under heat advisory watches or warnings from the National Weather Service, which is predicting that statewide records will be broken in Nevada and Arizona, along with hundreds of new daily record-high temperatures set in cities in the coming days. “This type of heat is unusual for the month of June,” said Julie Malingowski, a meteorologist with the National Weather Service (NWS), adding that most heatwaves that have historically affected the western US occurred in July and August. The triple-digit heat is expected to extend from Tuesday through Saturday in some areas, with little reprieve overnight, and the NWS Climate Prediction Center anticipates that temperatures will continue to be higher than normal through the summer. The heatwave has elevated wildfire concerns in the west, which is already in the grips of a drought disaster. Significant fire potential has been declared across six states by the National Interagency Fire Center, and the heat has the potential to drive strong gusty winds exceeding 40mph through the parched landscapes along the Pacific coast. “We are in the middle of a drought and the vegetation is stressed already,” Malingowski said, adding that fires start more easily and spread faster in hot, dry weather. Hundreds of thousands of acres have burned across the west and California has already passed last year – a record-breaking fire season when more than 4.2m acres burned – in terms of number of acres burned so far. The California power grid operator also issued warnings that the hot weather could stress the system and encouraged residents to conserve when possible. “Although no outages or other power disruptions are anticipated right now,” the California Independent System Operator (ISO) said in a statement, “ISO could take a number of actions to reduce demand and access additional energy.” Those without access to air conditioning will experience the worst of the heatwave, especially unhoused residents and other vulnerable populations, and there will be little reprieve from the oppressive heat overnight. “That’s the real danger with these heatwaves,” Malingowski said. “It is very, very hot during the day, of course, but the overnight temperatures aren’t getting cool enough to give that relief.” She encouraged residents across the region to stay indoors if they are able, hydrate and ensure that people and animals are not left to wait in cars, where fatalities can happen quickly. “That’s what causes the longer-term heat impacts.”