This blast of heat caps off a winter that barely felt like one in several South American countries — something also seen in other parts of the hemisphere. It’s also coming amid what will probably end up being the world’s toastiest September on record.

A heat dome of high pressure, this time focused over the south-central portion of the continent, has visited several times in recent months. In early August — midwinter — the Andes areas of Argentina and Chile saw temperatures rise into the mid-90s to around 100. Widespread record heat also swamped Paraguay and Brazil.

Boosted by the developing El Niño, a warming of equatorial waters in the Pacific Ocean that influences global weather patterns, the recurring heat dome has led to temperatures as much as 30 to 40 degrees above normal in the past. It is apparently set to do so again.

The latest flex of high heat could threaten records late Thursday across northern Argentina and into Paraguay. Extreme heat becomes a good bet by Friday, lasting into early next week. With time, it expands to cover Paraguay through southern Brazil. As cooler air drifts northward to start the week, high heat focuses on southeast Brazil before waning somewhat.

Daily maximum temperatures of 110 to 120 degrees are anticipated. Widespread highs at or above 104 degrees are as well.

Records for Brazil and Paraguay are 112.6 degrees (44.8 C) and 113 degrees (45 C), respectively, according to MetSul Meteorologia, a weather firm in Brazil.

Southern hemisphere winter warmth

The southern hemisphere’s winter tends to be mild compared to that in the north. Repeated rounds of heat this year have been exceptional. They have not only impacted South America but also Africa and Australia as well as parts of Oceania.

Many of these locations are under siege yet again:

• New Zealand just saw its hottest September temperature since 1950, and the third-highest on record, with the 85.3 degrees observed in Wairoa, according to NIWA Weather, a weather organization based in Aukland.
• Australia is seeing night after night of record warm minimums for September, after a slew of similar highs. Widespread record highs at or above 104 degrees are expected in the days ahead.
• Southern Africa saw a resumption of extreme heat last week. Temperatures have risen to near 104 degrees in swaths of Zambia, Botswana and South Africa, including relatively high elevations up to around 3,500 feet above sea level.

It’s been a hot September

Despite this year easily keeping pace to be the hottest on record for the planet, September has still managed to assert itself.

“We will almost certainly see the hottest September on record,” wrote climate scientist Zeke Hausfather. “[M]ay well see the highest anomaly (deviation from normal) in what is already an exceptionally hot summer/early fall.”

While global heat is boosted by the strengthening El Niño over the Pacific Ocean, more broadly, oceans have been quite warm for years and recent heat waves have exhibited behaviors — including extremeness and longevity — that are consistent with expectations from climate change.

With El Niño peaking this winter, amplified warming associated with it is likely to persist through 2024.