This story was originally published by the Guardian and is reproduced here as part of the Climate Desk collaboration. A brutal and long-lasting heatwave is threatening to wreak havoc across the US west this week, as sweltering conditions, power shutoffs and a severe uptick in wildfire risks coincide with Fourth of July celebrations. Nearly 90 million people were under heat alerts from the National Weather Service (NWS) on Tuesday morning, as swaths of the south-central and western US were scorched.