Australia Weather News

Steve Absolum has certainly noticed the increased number of muggy days over summer.

"When I was a kid growing up, I don't remember humidity," the Wagga Wagga local said.

"Now we get near coastal weather."

Bureau of Meteorology senior hydrologist Masoud Edraki said it was not just the Riverina region feeling the moisture, with most of the state seeing a rise in relative humidity in the past 20 years.

"It's mostly across the board, with some exceptions in the very far east or north-east," he said.

"It's sensible humidity. You can feel it yourself that the humidity has increased."

The BOM's observations of weather patterns indicate an increase in relative humidity, or the amount of water vapour in the air.

Dr Edraki said one of the contributing factors to rising humidity and recent large rainfall events in ordinarily drier locations was warming sea surface temperatures.

"Onshore moisture [moves] to the land from the sea, and that's how it affects the intensity of rainfall as we have seen," he said.

A change in the air

Mr Absolum has spent his career installing air conditioning throughout the Riverina and said with increased humidity, another trend had formed.

"You go back 10 years ago, we were 80 per cent evaporative cooling installations, 20 per cent reverse cycle," he said.

But now his team would do about 350 jobs in a year, 50 involving evaporative cooling, affectionately known as a "swampy".

The rest are refrigerated units.

"They have completely flipped," he said.

Evaporative cooling draws in hot air from outside and passes it through water-soaked pads, which creates a cool humidity in the home.

As relative humidity increases, their efficiency decreases.

Mr Absolum said customers were moving away from the swampy because of its reduced efficiency in a more humid climate.

He said it was also because it added moisture to the home, bringing the potential of mould.

"Even in my own house, water on the walls, on the floors … that's where mould eventuates," he said.

Mould grows when moisture combines with dust particles.

While decreasing humidity in the home may help, it's not just evaporative coolers that cause mould to grow.

Building biologist Nicole Bijlsma said how people used their cooling systems was a bigger factor rather than the type of unit installed, as both cooling systems could increase mould in the home.

"[Servicing either type of unit] in a humid environment like Sydney should be done at least twice a year," she said.

"In a dry environment, [it should be serviced] before you turn it on at the beginning of summer."

Dr Bijlsma said this would lessen the "high levels of cladosporium, aspergillus [and] penicillium [fungi] throughout the home" that may be laying dormant in the system.

She said excess moisture could build up in the home if the cooling unit had "the temperature down too low or [when] the split system is too big for the room".

Dr Bijlsma recommended people be mindful of their "dust load" in order to combat mould.

"Think about getting a good vacuum cleaner with a HEPA filter, vacuuming the surface, followed through with a damp microfibre cloth to which you've dipped into a bit of detergent water, and then vacuum again" she said.

"It's in everyone's home — you're not special if you think you've got it, because we all do."