Oh the humidity: This could be the new norm for Brisbane

Brisbane is not just hot, it’s muggy. Really muggy. Yes, we live in a subtropical city, but you could be forgiven for feeling as though you have trekked through a South-East Asian jungle by the time you walk from the bus stop to your office in the morning.

Brisbane at this time of year usually means hot days, punctuated with a heat-busting afternoon thunderstorm, typically right on school pick-up time.

It has been a humid start to summer.Credit: William Davis

But so far, this December (and much of November) has been a much stickier experience than usual. Escaping the heat and humidity has not been easy, with many relying on running their air-conditioners day and night.

Brisbane’s humidity has reached 80 per cent in the past fortnight. On Monday morning, the humidity was 70 per cent, despite the temperature being under 30 degrees.

The dew point – a more accurate measure of the humidity – has been between 22 and 24 degrees, which is more akin to Cairns and Darwin than the River City.

This sticky start to summer could be the new norm for Brisbane, Bureau of Meteorology forecaster Livio Regano said.

So what’s causing it?

In short, it is rising sea temperatures and more specifically, hot air blowing in from the Coral Sea, Regano said.

“This year, the Coral Sea — from which the wind is currently blowing — is warmer than usual,” he said.

“The Coral Sea is hotter than it should be and this may well be the new normal.

“Our prevailing [summer] wind is usually from the south-east, blowing over from the cooler climes of New Zealand, and the cooler waters of the Tasman before it gets to us.

“But that’s not happening this year. It’s coming from the tropical ocean, not the temperate ocean, and that’s making all the difference.”

Brisbane typically relies on a cool sea breeze to provide relief from the summer heat, Regano said.

“Normally when you get a breeze from the ocean, it’s refreshing. When the ocean is really hot, you don’t get much relief. We’ve had a sea breeze for the last two weeks, but we haven’t had any relief at all, particularly at night,” he said.

The humidity makes for uncomfortable nights, he added.

“The water vapour acts like a blanket and stops the nights from cooling down as they should,” he said.

“The theme for this whole next week will be high humidity and very hot nights.”

Overnight temperatures are forecast to be 24 degrees this week, up from the December average of 20 degrees.

“Hot nights go hand-in-hand with high humidity,” Regano said.

Muggy air disrupts the body’s most important cooling technique – sweating – because it’s harder for beads of sweat to evaporate off the skin. That’s why we feel the temperature more acutely when it’s humid.

There is an increasing body of evidence that people find it harder to think straight on hot, humid days.

Exam scores can plunge by 14 per cent on 32-degree days. Productivity begins to slump when offices hit 26 degrees. In one experiment, university students languishing in a Boston heatwave were 13 per cent slower to crack simple word games, compared to peers who lived in air-conditioned dorms.

The specific effect of humidity on mood and behaviour is less well-studied than temperature.

But in 2016, NSW researchers found that people in humid conditions were more likely to report intense psychological distress. The results showed the harmful effect of heat on distress is approximately doubled under extreme humidity, and each uptick in humidity resulted in thousands more people reporting high psychological distress.

with Angus Dalton

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