Arizona county probes 53 suspected heat wave deaths in a week

Website data shows Arizona's Maricopa county is investigating 53 suspected heat wave deaths over the week to June 19, when record-shattering temperatures across the U.S. Southwest threatened to push power systems to the brink of failure.

As the Oregon cities of Portland and Salem and Seattle in Washington set new temperature records on Monday, fuelled by a heat wave in the Pacific Northwest, data on the Arizona county's website showed a jump in deaths under investigation.

A total of 73 deaths is being investigated over the week to June 19, up from 20 by the end of the previous week.

Three deaths in the county of more than 4.5 million people had been confirmed to be heat related until June 19.

County authorities were not immediately available for further comment.

The Arizona Daily Star quoted four climate scientists as saying climate change caused by human activity was probably behind the heat wave, which capped years of drought to strain California and Texas power grids and spread wildfires.

"I'd be very surprised if we do studies on the recent one, or the one about to unfold, and we didn't find an increased likelihood or severity of that heat wave due to climate change," UCLA scientist Daniel Swain told the paper about the waves.

The heat wave of the June 19 week was consistent with forecasts of more frequent, more extreme incidents long made by many climate-related computer models, said Michael Crimmins, an environmental scientist at the University of Arizona.