Electricity prices surged by nearly twice as much as overall inflation across the United States, new federal data show, putting life-saving air conditioning out of reach for a growing number of Americans struggling to pay utility bills.

The average cost of electricity bills last month rose by 4.4% compared to June of last year, surpassing overall economy-wide inflation of 3%, according to the latest consumer price index data the Bureau of Labor Statistics released Thursday.

While prices fell compared to May, only the cost of housing and transportation services saw a bigger yearly jump than electricity. The price of natural gas piped into homes for heating and cooking increased by 3.7% compared to the same period last year.

The price surge comes as brutal heat waves roast broad swaths of the U.S. and the globe, as the combined effect of climate change and El Nio weather cycles send global temperatures to new heights.

The National Weather Service already identifies extreme heat as the countrys No. 1 weather-related killer. And thats undercounting the number of deaths linked to overheating, say researchers, who warn that official data and underdeveloped reporting methods fail to capture the full toll.