CHICAGO • A brutal cold spell that paralysed the United States Midwest, freezing water mains, causing power outages and cancelling flights, has eased, with forecasts predicting a rapid thaw.
The past few days of intense cold from the so-called polar vortex that descended on the US Midwest and Northeast will go down in memory for its scenes of winter at its most bitter.
US media reported as many as 21 weather-related deaths since a snow storm hit the Midwest early last week, followed by plunging temperatures on Wednesday and Thursday. Temperature readings nosed up on Friday and "will continue to moderate", the National Weather Service said.
The concern, though, turned to the threat of flooding and further stress on already strained infrastructure as the region thawed out.
"In some areas of the Midwest, the coming wild temperature swing will be the most extreme warm-up from record winter cold ever seen in such a short-time period," Mr Jeff Masters, meteorologist at Weather Underground, told AFP.
The Arctic air mass that veered off its normal polar route broke more than 340 records in communities across a cluster of states, according to the Midwestern Regional Climate Centre. With wind chill factored in, temperatures dropped below minus 50 deg C in several states.
By tomorrow, the weather was expected to be comparatively balmy - around 10 deg C in Chicago and Detroit.
"It's important to remember that the rapid change in weather and snow melt could lead to dangerous flooding," Mr James Joseph, regional director of the Federal Emergency Management Agency, said in a statement.
But while the US Midwest and East Coast thawed out, a fierce winter storm was headed towards California, carrying heavy rain and high winds that could touch off city flooding and mudslides.
Though the sun was out in Los Angeles on Friday afternoon and temperatures hovered around 15 deg C, the National Weather Service (NWS) said rain would begin to fall later in the evening and continue without let-up through Saturday night.
"This is a very big storm coming through Southern California" from the eastern Pacific Ocean, said NWS meteorologist Rich Thompson.
The NWS predicted up to 7.6cm of rain in coastal and valley areas with 18cm to 20cm forecast for mountain areas. Central and Northern California were also expected to be hit by rain and high winds.
Mr Thompson said the weather service was not expecting the rain to be significant and sustained enough to cause widespread, damaging mudslides in areas left blackened and denuded of trees by major California wildfires late last year.
AGENCE FRANCE PRESSE, REUTERS