At least 70 large wildfires are burning across the US west and nearby states – engulfing more than 1m acres in flames – as fears mount that shifting conditions can worsen an already dire situation. Significant areas of these states are in the grips of drought conditions that are considered “extreme” and “exceptional” – the most severe categories. Authorities in Oregon have said that these arid, windy and unstable conditions will continue fueling the 281,208-acre Bootleg fire, which is just 22% contained, according to National Interagency Fire Center and InciWeb. The smoke and heat have spurred giant “fire clouds”, which are dangerous columns of ash and smoke that can spiral up to six miles skyward. At least 2,106 firefighting personnel are battling Bootleg, which is now the largest US forest fire. Officials have also worried that this inferno might merge with the nearby Log fire, which totals at least 4,830 acres. Meteorologists also detected a larger, more extreme type of fire clouds earlier this week – ones that can make their own weather, such as “fire tornadoes”. This extreme fire behavior is expected to worsen over the course of this weekend. “Fire remains very active with significant acreage increases due to hot, dry and breezy conditions, and plume-dominated fire behavior. Poor humidity recovery at night is contributing to active fire spread through the night time period,” InciWeb said of Bootleg. “Robust spread rates are being generated by drought-affected fuels. Expecting similar conditions for the next several days.” “This fire is large and moving so fast, every day it progresses four to five miles,” Bootleg’s incident commander, Joe Hassel, said. “One of the many challenges that our firefighters face every day is working in new country that can present new hazards all the time.” The National Weather Service (NWS) has forecast “excessive heat” throughout the northern plains and intermountain west states, with temperatures soaring “well above average” over the next several days. The NWS said that triple-digit highs can be expected through eastern Montana and lower elevations of the intermountain west. “This heat wave will exacerbate the severe to exceptional drought currently found across the region, which in combination can make for an environment ripe for wildfires to spread uncontrollably,” the NWS said. The service also warned that “dry lightning could be a concern” for portions of northern and central California on Sunday. While monsoonal moisture is entering from the south, very little rain will be produced. Residents of the northern California municipality of Paradise, which was mostly razed during a 2018 wildfire that left 85 dead, are on alert because of a fire which is some 15 miles north-east of the town. The extremely hot, dry conditions fanning these fires are linked to human-caused climate change. The US west has grown much drier and warmer over the past three decades and is expected to grow more extreme which, in turn, is poised to create more frequent and destructive wildfires. According to the National Interagency Fire Center, there have been 34,596 wildfires tallied from 1 January to 16 July, affecting 2,364,643 acres. Over the same period of 2020, there were 28,423 wildfires affecting 1,778,583 acres.