A scorching heat wave searing the United States was expected to ease soon, meteorologists said Saturday, heralding relief from record highs blamed for deaths and drought-like conditions.

Across the country, at least two dozen fatalities are tied to the extreme period of hot weather, one of the longest and hottest on record, according to media reports.

Blistering temperatures will cool "significantly" over the weekend and were forecast to be below average by Monday as a cold front pushed south from Canada to the central and eastern United States, the National Weather Service said.

But the breather will likely be accompanied by fierce storms, forecasters warned, possibly spelling disaster for states still recovering from a killer band of thunderstorms that wreaked havoc last week, leaving millions without air conditioning or refrigeration after power cuts.

"Severe weather, including damaging wind, is expected to accompany this cold front," the weather service said, adding later that hail and isolated tornadoes could not be ruled out.

A week after the devastating June 29 thunderstorms, 416,192 customers in West Virginia, Virginia, Ohio, New Jersey, Maryland and Indiana were still off the power grid -- down from several million -- according to the latest Energy Department update issued Friday.

Ten deaths are tied to the heat wave in Chicago, Illinois, with the neighboring state of Wisconsin reporting at least three fatalities, local media reported.

In Ohio, where another three deaths are being blamed on the weather, the health department urged citizens to check up on each other.

"Ohioans are in this heat wave together!" it said on its website.

"Reach out and make sure those around you -- neighbors, family, church members or customers in your business -- have the tools they need to stay healthy and be safe."

With temperatures still soaring as the weekend kicked off, authorities urged caution to avoid heat-related health problems.

In Chicago, where the mercury has hit 100 degrees Fahrenheit (38 Celsius) for the past three days, an extreme heat warning that had been set to expire Friday evening was extended until late Saturday, the Chicago Tribune reported.

Hours at public swimming pools in the capital Washington meanwhile were expanded to provide a refuge for people trying to stay cool as temperatures hit their peak on Saturday.

Just minutes from the White House, 35-year-old Sarah Washington and her eight-year-old daughter Raquia sold cold water bottles in an effort to raise money for neighbors hit by recent storm-related power outages.

"We're just trying to help a few families," said Washington as she sought shelter from the sun at a bus stop.

Record-breaking temperatures have lasted several weeks. Over the past 30 days, more than 4,500 daily record highs have been recorded around the country, according to CNN.

Meteorologists blame the sweltering weather on a huge heat dome over large swathes of the country. High-pressure air in the domes blocks cooling winds, setting hot temperatures, higher humidity and very little breeze underneath.

Coupled with a drought in certain areas, the blistering heat has also taken a toll on US farmland.

"In the primary growing states for corn and soybeans, 22 percent of the crop is in poor or very poor condition, as are 43 percent of the nation's pastures and rangelands and 24 percent of the sorghum crop," the US Drought Monitor said in its latest update issued earlier this week.