SANTIAGO, Chile (AP) — Chileans are bundling up for their coldest autumn in more than 70 years mere days after sunning in T-shirts — a dramatic change of wardrobe brought on this week by a sudden cold front gripping portions of South America unaccustomed to bitter wind chills this time of year.

Temperatures broke records along the coast of Chile and in Santiago, the capital, dipping near freezing and making this month the coldest May that the country has seen since 1950, the Chilean meteorological agency reported.

An unusual succession of polar air masses has moved over southern swaths of the continent, meteorological experts say, pushing the mercury below zero Celsius (32 Fahrenheit) in some places. It's the latest example of extreme weather in the region — a heat wave now baking Mexico, for instance — which scientists link to climate change.

“The past few days have been one of the longest (cold fronts) ever recorded and one of the earliest ever recorded" before the onset of winter in the Southern Hemisphere, said Raul Cordero, a climatologist at Santiago University. “Typically the incursions of cold air from the Antarctic that drive temperatures below zero occur from June onwards, not so much in May."

The cold front sweeping in from Antartica has collided with warm air pushing in from the northwestern Amazon, helping fuel heavy rainstorms battering Brazil, according to that country's National Meteorological system.

Chile's government issued frosty weather alerts for most of the country and ramped up assistance for homeless people struggling to endure the frigid temperatures on the streets. Snow cloaked the peaks of the Andes and fell in parts of Santiago, leading to power outages in many areas this week.

“Winter came early,” said Mercedes Aguayo, a street vendor hawking gloves and hats in Santiago.

She said she was glad for a boost in business after Chile's record winter heat wave last year, which experts pinned on climate change as well as the cyclical El Niño weather pattern.

“We had stored these goods (hats and gloves) for four years because winters were always more sporadic, one day hot, one day cold,” Aguayo said.

This week's cold snap also took parts of Argentina and Paraguay by surprise.

Energy demand soared across many parts of Argentina. Distributors cut supplies to dozens of gas stations and industries in several provinces to avoid outages in households, the country's main hydrocarbon company, CECHA, said Thursday.