Summer-like heat is scorching the Southern Hemisphere — in winter

It’s winter in the Southern Hemisphere — but you wouldn’t know it from the thermostat.

On August 26, a remote stretch of the coastline in Western Australia experienced the highest winter temperature ever recorded anywhere in the country: a blistering 41.6° Celsius (107° Fahrenheit).

In Bidyadanga, an Aboriginal community in Western Australia, the overnight low temperature on August 28 was a staggering 27.2° C (81° F). That’s in winter, when the long-term average nighttime temperature has been around 15° C (59° F). Such heightened nighttime temperatures can disrupt sleep, leading to decreased cardiovascular and mental health (SN: 8/6/23).

These are some of the most extreme numbers in a month of extremes for the land down under, which has sweltered under a prolonged winter heat wave that threatens to break the country’s record for average winter temperatures — a record set just last year. In 2023, Australia’s average winter temperature was 1.53 degrees C above the long-term average of 14.96° C from 1961 to 1990, and the highest since recordkeeping began in 1910.

Globally, average nighttime temperatures are increasing even faster than daytime temperatures, a phenomenon scientists call “asymmetric warming.” That nighttime warming is a big factor in pushing the planet’s average temperature upward, contributing to its 14-month streak of record-breaking heat (SN: 8/19/24).

Australia is not the only region in the Southern Hemisphere that’s sweltering. Brazil’s vast Pantanal wetlands, bordering Bolivia and Paraguay, are on fire — literally — thanks to a one-two punch of severe droughts and unseasonably warm temperatures. Raging megafires have burned over 700,000 hectares of the Pantanal this year.

Winter has in the past brought dry and mild weather to the Pantanal. But that’s been changing. And in fact, the Southern Hemisphere has gotten increasingly dry over the last two decades, researchers reported in Science in 2023. The natural climate phenomenon El Niño is one major contributor; climate change may also be intensifying El Niño-linked rains and drought, particularly in the Southern Hemisphere (SN: 7/19/23)

These warmer winters can have negative impacts on food security, water supplies and insect populations. Reader Judy Dobles asked about the impact of heat on the ability to grow food. Warmer winters can change when plants germinate, and when they bear fruit. For instance, in the United States, where average winter temperatures are creeping upward too, that shift prompted the U.S. Department of Agriculture in 2023 to release a new plant hardiness zone map, used to recommend what plants will thrive in certain regions and when best to plant them.

“How do growers (agriculture and horticulture) plan for future production in a changing climate?” asks reader Brian Hesketh. Many efforts are under way to breed heat-tolerant plants, such as an apple bred to thrive at temperatures as high as 40° C (104° F) (SN: 8/22/24).

Warmer winters can also mean less snowpack to feed rivers and recharge groundwater. And cold weather helps keep insect-borne diseases, such as dengue, in check (SN: 8/26/24). 

As always, please keep sending in your questions about Earth’s extreme climate records. Thank you!