Heat wave a climate warning

An unusually early and longlasting heat wave brought more triple-digit temperatures in the Fahrenheit scale yesterday to a large swath of the US West, raising concerns that such extreme weather could become the new normal amid a decades-long drought.

Phoenix, which is seeing some of the highest temperatures this week, tied a record for the second day in a row when it reached 115 degrees Fahrenheit – 46 degrees Celsius – yesterday and was expected to hit 47C each of the next two days, the National Weather Service said.

Scientists who study drought and climate change say that people living in the American West can expect to see more of the same in the coming years.

‘‘Heat waves are getting worse in the West because the soil is so dry’’ from the region’s megadrought, said Park Williams, a University of California, Los Angeles, climate and fire scientist who has calculated that soil in the western half of the nation is the driest it has been since 1895. ‘‘We could have two, three, four, five of these heat waves before the end of the summer.’’

A few clouds were holding the temperatures down slightly in the desert region of southwest Arizona and southeast California, but there was no real relief expected from the excessive heat warning in effect until at least Monday.

In California, the operator of the state’s power grid is asking residents to voluntarily conserve power for a few hours today evening as record-breaking heat blankets the West this week.

The California Independent System Operator issued the alert to help relieve stress on the grid. It asks people to set thermostats to 25C or higher, turn off unnecessary lights and avoid using major appliances. Chief executive Elliot Mainzer said the grid was stable and there was no expectation of rotating power outages, but that could change as temperatures spike in the coming days.

Elsewhere in the West, tripledigit heat was forecast in Denver, which saw a record high of 101F, 38C, on Wednesday.

The weather service issued an excessive heat warning for parts of western Colorado, much of which is experiencing extreme drought conditions.

New Mexico also experienced more record-breaking highs. But a possible respite was in sight with showers and thunderstorms expected in parts of the state.

In Montana, temperatures over 38C have made it tougher to fight wildfires that have exploded in size, triggering evacuations and destroying an undetermined number of homes. Furious winds have stoked the flames and forced the crash-landing of a firefighting helicopter. At least 14 new fires have been reported in Montana and Wyoming since Wednesday.

The dry weather was also being felt in Idaho, where authorities are preparing for what could be a challenging wildfire season.

Nick Nauslar, a meteorologist with the National Interagency Fire Centre, told state officials this week that nearly 80 per cent of Idaho is in drought and the rest will likely experience it in the coming months. Idaho had its second-driest spring in the last 126 years.